Interim Photochemical Modeling Report

Transcription

1 FY14-15 PGA FY14-2 Task 3.1 Amendment 2 Interim Photochemical Modeling Report Evaluation of Potential Ozone Impacts from Proposed Electric Generating Units at Tradinghouse and Lake Creek Power Plants in McLennan County PREPARED UNDER A GRANT FROM THE TEXAS COMMISSION ON ENVIRONMENTAL QUALITY The preparation of this report was financed through grants from the State of Texas through the Texas Commission on Environmental Quality. The content, findings, opinions and conclusions are the work of the author(s) and do not necessarily represent findings, opinions or conclusions of the TCEQ. Prepared for: Falen Bohannon The Heart of Texas Council of Governments 1514 S. New Road Waco, TX Prepared by: Sue Kemball-Cook, Jeremiah Johnson, John Grant and Greg Yarwood Ramboll Environ US Corporation 773 San Marin Drive, Suite 2115 Novato, California, P F August 2015

2 CONTENTS LIST OF ACRONYMS AND ABBREVIATIONS EXECUTIVE SUMMARY INTRODUCTION EMISSIONS Development of Emissions for Photochemical Modeling Tradinghouse Power Plant Emissions Scenario Development Lake Creek Power Plant Emissions Scenario Development Emissions Modeling PHOTOCHEMICAL MODELING Modeling Method CAMx Direct Decoupled Method Probing Tool TCEQ 2012 Modeling Platform Ozone Modeling Results DDM Ozone Sensitivity Results Ozone Impact Analysis SUMMARY REFERENCES TABLES Table 1-1. NOx emissions summary for high EGU utilization scenarios Table 1-2. Summary of daily maximum 8-hour average (MDA8) ozone impacts at Waco Mazanec monitor (CAMS 1037) for high EGU utilization scenarios. Simple cycle is abbreviated SC and combined cycle is abbreviated CC Table 3-1. Tradinghouse turbine normal operating emissions in simple and combined cycle modes Table 3-2. Tradinghouse turbine startup and shutdown emissions Table 3-3. Tradinghouse hourly emissions from a single GE turbine for combined cycle and simple cycle emissions scenarios (lbs) i

3 Table 3-4. Tradinghouse hourly emissions from a single Siemens turbine for combined cycle and simple cycle emissions scenarios (lbs) Table 3-5. Tradinghouse emissions from non-turbine equipment sources Table 3-6. Tradinghouse hourly emissions from non-turbine equipment sources (same emissions for both simple cycle and combined cycle emissions scenarios) Table 3-7. Tradinghouse hourly emissions from all (turbines and non-turbine) equipment sources Table 3-8. Tradinghouse emissions summary Table 3-9. Lake Creek turbine normal operating emissions in simple cycle mode Table Lake Creek turbine startup and shutdown emissions Table Lake Creek hourly emissions from a single GE turbine Table Lake Creek hourly emissions from a single Siemens turbine Table Lake Creek emissions from non-turbine equipment sources Table Lake Creek hourly emissions from non-turbine equipment sources Table Lake Creek hourly emissions from all (turbines and non-turbine) equipment sources Table Lake Creek emissions summary Table Tradinghouse stack parameters Table Lake Creek stack parameters Table Tradinghouse VOC speciation by stack Table Lake Creek VOC speciation by stack Table 4-1. Summary of high utilization ozone season day emissions scenarios for Tradinghouse and Lake Creek Table 4-2. Summary of daily maximum 8-hour average (MDA8) ozone impacts at Waco Mazanec monitor (CAMS 1037) for high EGU utilization scenarios. Simple cycle is abbreviated SC and combined cycle is abbreviated CC) Table 5-1. Summary of high utilization ozone season day emissions scenarios Table 5-2. Summary of daily maximum 8-hour average (MDA8) ozone impacts at Waco Mazanec monitor (CAMS 1037) for high EGU utilization scenarios. Simple cycle is abbreviated SC and combined cycle is abbreviated CC) ii

4 FIGURES Figure 2-1. Location of the Waco Mazanec (CAMS 1037) monitor in McLennan County. TCEQ CAMS ozone monitor locations are shown as blue circles. (TCEQ figure) Figure 2-2. Location of proposed EGUs at the Tradinghouse and Lake Creek facilities in McLennan County and their distance from the Waco Mazanec (CAMS 1037) monitor Figure 3-1. Tradinghouse process flow diagram from NSR Permit Amendment Application Figure 3-2. Description of process flow at the Tradinghouse facility EGUs reproduced directly from p. 20 of NSR Permit Amendment Application Figure 3-3. Lake Creek process flow diagram from Lake Creek Permit Figure 3-4. Process flow description from Lake Creek Permit Figure 3-5. Temporal allocation of EGU emissions. Vertical axis shows the fraction of daily total emissions that are emitted during each hour of the day Figure 4-1. CAMx nested 36/12/4 km modeling domains for the 2012 episode Figure 4-2. DDM ozone sensitivity (ppb/tpd) of the episode maximum MDA8 ozone to Lake Creek (left panel) and Tradinghouse (right panel) emissions during the June 2012 episode. The HOTCOG counties are outlined in black and the location of the Waco Mazanec (CAMS 1037) monitor is indicated by an open circle. The City of Waco is indicated by a circle with a dot in the middle. The northernmost triangle shows the location of the Tradinghouse facility and the southernmost triangle indicates the Lake Creek facility Figure 4-3.Wind rose for days when MDA8>75 ppb at the Waco Mazanec (CAMS 1037) monitor Figure 4-4. Ozone impact analysis method Figure 4-5. Episode maximum MDA8 ozone impacts for Lake Creek high utilization scenario emissions during the June 2012 episode. SC indicates that the EGUs were assumed to be running in simple cycle (SC) mode. The HOTCOG counties are outlined in black and the location of the Waco Mazanec (CAMS 1037) monitor is indicated by an open circle. The City of Waco is indicated by a circle with a dot in the middle. The northernmost triangle shows the location of the Tradinghouse facility and the southernmost triangle indicates the Lake Creek facility iii

5 Figure 4-6. Episode maximum MDA8 ozone impacts for Tradinghouse high utilization scenario emissions during the June 2012 episode. CC indicates that the EGUs were assumed to be running in combined cycle (CC) mode (right panel). SC indicates that the EGUs were assumed to be running in simple cycle (SC) mode (right panel). Otherwise, as in Figure Figure 4-7. Episode maximum MDA8 ozone impacts during the June 2012 episode when both Tradinghouse and Lake Creek are operating. CC indicates that Tradinghouse EGUs were assumed to be running in combined cycle (CC) mode (right panel). SC indicates that Tradinghouse EGUs were assumed to be running in simple cycle (SC) mode (right panel). Lake Creek EGUs were operating in simple cycle in both scenarios. Otherwise, as in Figure Figure 4-8. As in Figure 4-7, with view expanded to show ozone impacts beyond the HOTCOG counties iv

6 LIST OF ACRONYMS AND ABBREVIATIONS CAMS CAMx CEM CO CTG DFW EGU EPA DV DVs EGU EPA HOTCOG Hr kw MDA8 NAA NAAQS NNA NO NO 2 NOx O 3 OSD ppb SCC SIC SIP SO 2 STARS STG TCEQ Ton tpd VOC yr Continuous Air Monitoring Station Comprehensive Air Quality Model with Extensions Continuous emissions monitor Carbon monoxide Combustion turbine generator Dallas-Fort Worth Electric generating unit Environmental Protection Agency Design value Design values Electric generating unit Environmental Protection Agency Heart of Texas Council of Governments Hour Kilowatt Daily maximum 8-hour average Non-Attainment Area (for the ozone NAAQS) National Ambient Air Quality Standard Near non-attainment area Nitric oxide Nitrogen dioxide Oxides of nitrogen Ozone Ozone season day Parts per billion Source classification code Standard industrial classification State Implementation Plan (for the ozone NAAQS) Sulfur dioxide State of Texas Air Reporting System Steam turbine generator Texas Commission on Environmental Quality English short ton (2000 pounds) Tons per day Volatile organic compound Year 1

7 1.0 EXECUTIVE SUMMARY In this study, we evaluated potential ozone impacts of recently-permitted and proposed new electric generating units (EGUs) at two facilities in McLennan County, TX. In 2014, the TCEQ granted New Source Review (NSR) Permit , which allows the Tradinghouse Power Company, LLC (Tradinghouse) to construct and operate two natural gasfired, simple-cycle combustion turbine generating units (CTGs) at the Tradinghouse facility near Hallsburg in McLennan County. These simple cycle CTGs will have a total generating capacity of approximately MW, depending on turbine model selection, and were permitted for peaking service as well as extended periods of operation or non-operation. The new CTGs will replace the two former EGUs at the Tradinghouse facility. These two lower-efficiency, natural gas-fired electric generation boilers (565 MW Unit 1 and the 818 MW Unit 2) were removed from service in 2010 and were dismantled in In 2015, Tradinghouse filed an amendment to Permit proposing to add a duct-fired heat recovery steam generator (HRSG) to each CTG as well as a common steam turbine generator (STG) and auxiliary equipment. This would add combined cycle capability to its alreadypermitted simple cycle CTG Units 1 and 2. Tradinghouse would retain the ability to operate Units 1 and 2 in simple cycle mode. ln addition, Tradinghouse proposed to add an additional set of CTGs, Units 3 and 4, as well as duct-fired HRSGs and a common STG so that Units 3 and 4 may also be used in either simple or combined cycle mode. The four new Tradinghouse CTG units together with the STG units would have a generating capacity of 1,140-1,274 MW. In 2014, the TCEQ granted NSR Permit , which allows the Lake Creek 3 Power Company LLC (Lake Creek) to construct and operate two natural gas-fired, simple-cycle CTGs at the Lake Creek facility near Riesel in McLennan County. The two simple cycle units will each provide ~230 MW for a total of ~460 MW, and were permitted for peaking service as well as extended periods of operation or non-operation. These two new CTGs will replace two lower-efficiency, natural gas-fired electric generation boilers (87 MW Unit 1 and the 230 MW Unit 2) that were retired in 2009 and dismantled in The new EGUs are intended to respond to the expected increase in demand for power along the Interstate 35 corridor due to projected population growth 3. The operation of the proposed EGUs at Tradinghouse and Lake Creek will result in new emissions of nitrogen oxides (NOx), a precursor to ozone, although NOx emissions from both facilities will be controlled. CTG NOx emissions will be reduced at both facilities through the use of dry low NOx combustors and Tradinghouse EGUs will further control NOx through ammonia injection/selective catalytic reduction when the units are operating in combined cycle mode. The Lake Creek Permit and

8 Tradinghouse Permit Amendment Applications indicate that these NOx emissions controls are consistent with Best Available Control Technology for natural gas-fired CTGs in Texas ozone attainment areas. The Heart of Texas Council of Government s (HOTCOG s) photochemical modeling and ambient data and emission inventory analyses have shown that ozone formation in the 6-county HOTCOG area is limited by the amount of available NOx. Additional NOx emissions may therefore result in additional local ozone formation. HOTCOG s conceptual model of ozone formation (McGaughey et al., 2010; 2012) indicates that the Tradinghouse and Lake Creek facilities are located in areas that are often upwind of the Waco Mazanec (CAMS 1037) ozone monitor in McLennan County on high ozone days. Assessments of ozone impacts of the new simple cycle units at Tradinghouse and Lake Creek were not required to be performed as part of the permitting process. Therefore, potential ozone impacts of the new simple cycle EGUS have not yet been evaluated. The HOTCOG 6-county area is an ozone Near Nonattainment Area (NNA). The National Ambient Air Quality Standard (NAAQS) for ozone is currently set at 75 ppb. The ozone design value for the Waco Mazanec monitor was 69 ppb at the end of 2014 and is currently in attainment of the NAAQS. On November 26, 2014, the EPA announced their proposal to lower the NAAQS to a value in the ppb range. Depending on where the NAAQS is set, the Waco Mazanec monitor could be very close to or out of compliance. An increase in NOx emissions in a region that is often upwind of the Waco Mazanec monitor on high ozone days has the potential to influence the attainment status of the Waco Mazanec monitor. Therefore, the HOTCOG Air Quality Advisory Committee (AQAC) has carried out this study to evaluate the potential ozone impacts of the new emissions from the permitted and proposed facilities. We performed photochemical modeling to evaluate the potential ozone impacts of NOx emissions from the new Tradinghouse and Lake Creek EGUs and ancillary facilities. We used the June 2012 ozone modeling databases developed by the Texas Commission on Environmental Quality (TCEQ) for air quality planning by Texas NNAs. The Comprehensive Air Quality Model with Extensions (CAMx; Ramboll Environ, 2015) ozone model Decoupled Direct Method (DDM) probing tool was used to determine the sensitivity of ozone to NOx emissions from the new Tradinghouse and Lake Creek EGU and ancillary facilities. The DDM was used for this analysis because it can efficiently look at ozone impacts for different emissions scenarios. We evaluated ozone impacts of several different emissions scenarios. To determine the maximum potential ozone impacts, we used DDM to examine maximum utilization scenarios in which the Lake Creek and Tradinghouse facilities were assumed to be operating all CTGs for 24 hours/day on an ozone season day. For Tradinghouse, we developed anemissions scenario in which all four CTGs are operating in simple cycle mode and an emissions scenario in which all four CTGs are operating in combined cycle mode. Lake Creek CTGs will operate in simple cycle mode only, so only one emission scenario was developed for this facility. NOx emissions for 3

9 each maximum utilization scenario are shown in Table 1-1. We evaluated ozone impacts from the Lake Creek and Tradinghouse facilities operating alone and in combination. Table 1-1. NOx emissions summary for maximum EGU utilization scenarios. The ozone modeling indicated that emissions from the permitted/proposed EGUs at Tradinghouse and Lake Creek are predicted to increase ozone in McLennan County. In the June 2012 episode, the DDM analysis of NOx emissions from the Tradinghouse maximum utilization emissions scenario showed ozone impacts at Waco monitor of 1.06 ppb when all four CTGs were run in SC mode and 0.18 ppb when all four CTGs were run in combined cycle mode. For Lake Creek, the DDM analysis of the maximum utilization emissions scenario ozone impacts at Waco monitor were 1.04 ppb with both CTGs running in simple cycle mode. We also evaluated the combined impacts of the two facilities for the cases where all four Tradinghouse EGUs were operating in either simple cycle or combined cycle modes. Ozone impacts estimated by the DDM tool for the maximum utilization scenario at the Waco Mazanec monitor are summarized in Table 1-2. Table 1-2. Summary of daily maximum 8-hour average (MDA8) ozone impacts at Waco Mazanec monitor (CAMS 1037) for maximum EGU utilization scenarios. Simple cycle is abbreviated SC and combined cycle is abbreviated CC. Although winds in this June 2012 episode are representative of winds on high ozone days at the Waco Mazanec (CAMS 1037) monitor, ozone impacts for a different time period could be higher or lower. We evaluated ozone impacts away from the Waco Mazanec monitor. With both facilities operating at our maximum utilization scenario, maximum impacts on the maximum daily 8- hour average (MDA8) ozone in the vicinity of the City of Waco range from 1-4 ppb, depending on whether all four Tradinghouse CTGs were run in simple cycle (4 ppb) or combined cycle (1 ppb) mode. With both facilities operating, ozone impacts > 1 ppb extended northward into the Dallas-Fort Worth (DFW) Nonattainment Area. When all four Tradinghouse CTGs were operating at our maximum utilization scenario in simple cycle mode, there were maximum MDA8 ozone impacts > 2 ppb in the vicinity of the Cleburne (CAMS 77) monitor and MDA8 4

10 ozone impacts > 3 ppb extending southward into Bell County in the vicinity of the Temple Georgia (CAMS 1045) monitor. 5

11 2.0 INTRODUCTION In this study, we evaluated potential ozone impacts of recently-permitted and proposed new electric generating units (EGUs) at two facilities in McLennan County, TX. In 2014, the TCEQ granted New Source Review (NSR) Permit , which allows the Tradinghouse Power Company, LLC (Tradinghouse) to construct and operate two natural gasfired, simple-cycle combustion turbine generating units (CTGs) at the Tradinghouse facility near Hallsburg in McLennan County. These simple cycle CTGs will have total generating capacity of approximately MW, depending on turbine model selection, and were permitted for peaking service as well as extended periods of operation or non-operation. The new CTGs will replace the two former EGUs at the Tradinghouse facility. These two lower efficiency natural gas-fired electric generation boilers (565 MW Unit 1 and the 818 MW Unit 2) were removed from service in 2010 and were dismantled in In 2015, Tradinghouse filed an amendment to Permit proposing to add a duct-fired heat recovery steam generator (HRSG) to each CTG as well as a common steam turbine generator (STG) and auxiliary equipment. This would add combined cycle capability to its alreadypermitted simple cycle CTG Units 1 and 2. Tradinghouse would retain the ability to operate Units 1 and 2 in simple cycle mode. ln addition, Tradinghouse proposed to add an additional set of CTGs, Units 3 and 4, as well as duct-fired HRSGs and a common STG so that Units 3 and 4 may also be used in either simple or combined cycle mode. The four new Tradinghouse CTG units together with the STG units would have a generating capacity of 1,140-1,274 MW. In 2014, the TCEQ granted NSR Permit , which allows the Lake Creek 3 Power Company LLC (Lake Creek) to construct and operate two natural gas-fired, simple-cycle CTGs at the Lake Creek facility near Riesel in McLennan County. The two simple cycle units will each provide ~230 MW for a total of ~460 MW, and were permitted for peaking service as well as extended periods of operation or non-operation. These two new CTGs will replace two lower efficiency natural gas-fired electric generation boilers (87 MW Unit 1 and the 230 MW Unit 2) that were retired in 2009 and dismantled in The new EGUs are intended to respond to the expected increase in demand for power along the Interstate 35 corridor due to projected population growth 6. The operation of the proposed EGUs at Tradinghouse and Lake Creek will result in new emissions of nitrogen oxides (NOx), a precursor to ozone, although NOx emissions from both facilities will be controlled. CTG NOx emissions will be reduced at both facilities through the use of dry low NOx combustors and Tradinghouse EGUs will further control NOx through ammonia injection/selective catalytic reduction when the units are operating in combined cycle mode

12 The Heart of Texas Council of Government s (HOTCOG s) photochemical modeling and ambient data and emission inventory analyses have shown that ozone formation in the 6-county HOTCOG area is limited by the amount of available NOx. Additional NOx emissions may therefore result in additional local ozone formation. The HOTCOG 6-county area is an ozone Near Nonattainment Area (NNA). The National Ambient Air Quality Standard (NAAQS) for ozone is currently set at 75 ppb. The Texas Commission on Environmental Quality (TCEQ) operates a Continuous Air Monitoring Station (CAMS) ozone monitor in McLennan County; this is the Waco Mazanec monitor (CAMS 1037). The location of the monitor is shown in Figure 2-1 and the locations of the new facilities at Tradinghouse and Lake Creek are shown in relation to the Waco Mazanec monitor in Figure 2-2. The ozone design value for the Waco Mazanec monitor was 69 ppb at the end of 2014 and is currently in attainment of the NAAQS. On November 26, 2014, the EPA announced their proposal to lower the NAAQS to a value in the ppb range. Depending on where the NAAQS is set, the Waco Mazanec monitor could be very close to or out of compliance. HOTCOG s conceptual model of ozone formation (McGaughey et al., 2010; 2012) indicates that the Tradinghouse and Lake Creek facilities are located in areas that are often upwind of the Waco Mazanec ozone monitor in McLennan County on high ozone days. Assessments of ozone impacts of the currently permitted units at Tradinghouse and Lake Creek were not required to be performed as part of the permitting process. Therefore, potential ozone impacts of the new EGUS have not yet been evaluated. An increase in NOx emissions in a region that is often upwind of the Waco Mazanec monitor on high ozone days has the potential to influence the attainment status of the Waco Mazanec monitor. Therefore, the HOTCOG Air Quality Advisory Committee (AQAC) has carried out this study to evaluate the potential ozone impacts of the new emissions from the permitted and proposed facilities. We performed photochemical modeling to evaluate the potential ozone impacts of emissions from the permitted/proposed Tradinghouse and Lake Creek EGUs and ancillary facilities. We used the June 2012 ozone modeling databases developed by the Texas Commission on Environmental Quality (TCEQ) for air quality planning by Texas NNAs. The Comprehensive Air Quality Model with Extensions (CAMx; Ramboll Environ, 2015) ozone model Decoupled Direct Method (DDM) probing tool was used to determine the sensitivity of ozone to NOx emissions from the permitted/proposed Tradinghouse and Lake Creek EGU and ancillary facilities. This report describes the emissions estimation method and results (Section 3.1), emissions modeling (Section 3.2) and ozone modeling methods and results (Section 4). Section 5 provides a summary of the results of the study. 7

13 Figure 2-1. Location of the Waco Mazanec (CAMS 1037) monitor in McLennan County. TCEQ CAMS ozone monitor locations are shown as blue circles. (TCEQ figure 7 )

14 Figure 2-2. Location of permitted/proposed EGUs at the Tradinghouse and Lake Creek facilities in McLennan County and their distance from the Waco Mazanec (CAMS 1037) monitor. 9

15 3.0 EMISSIONS In Section 3, we describe the development of emission inventories for photochemical modeling for the permitted and proposed new EGUs and ancillary facilities at Lake Creek and Tradinghouse. 3.1 Development of Emissions for Photochemical Modeling For the photochemical modeling using the TCEQ s June 2012 modeling episode, we developed emissions for an ozone season day for Tradinghouse and Lake Creek. Through a review of the permitted emissions and operating modes in Lake Creek NSR Permit and Tradinghouse Permit Amendment Application, we developed emissions for a peaking scenario in which all EGUs at each facility are operating as peaking units. We assumed that when both facilities are operating, all EGUs at both sites are fully utilized and operating at their maximum short term emissions rate. We developed the peaking emissions scenario for both Tradinghouse and Lake Creek emissions of the ozone precursors NOx, volatile organic compounds (VOC) and carbon monoxide (CO) for the permitted/proposed EGUs and ancillary facilities during an ozone season day. For Tradinghouse, we developed the peaking emissions for CTGs operating in both simple cycle and combined cycle mode. For Lake Creek, only peaking emissions in simple cycle mode were required, as this facility does not have combined cycle capability Tradinghouse Power Plant Emissions Scenario Development Figure 3-1 shows the process flow diagram for a single EGU from the Tradinghouse permit amendment application. The diagram shows the different emissions point number (EPNs) locations that appear in the emissions calculations in the Tradinghouse Permit Amendment Application. Figure 3-2 is the text from the Permit Amendment Application that summarizes the operation of the CTG and explains the difference in routing of the CTG exhaust in simple cycle mode versus combined cycle mode. In simple cycle mode, the CTG exhaust is emitted directly from the stack and there is no extraction of energy from the waste heat in the exhaust. About 30% of the energy of the fuel is used in simple cycle mode. An advantage of running the CTGs in simple cycle mode is that the EGUs can be started up quickly and can respond rapidly to requests by the grid operator for more electricity. This is why simple cycle units are often used as peaking units for a limited number of hours, and not for continuous operation. In combined cycle mode, the CTG exhaust is routed through a HRSG and additional energy is extracted from the waste heat to make steam and run a second generator, the STG, before exhausting through a separate stack. In combined cycle mode, more energy is extracted from the fuel (~60%) so that a combined cycle unit is more efficient than a simple cycle unit, and is the preferred operating mode for continuous operation. NOx emissions are lower in combined cycle mode than in simple cycle mode because of the presence of the ammonia injection/scr NOx control equipment in the HRSG unit. As the CTG exhaust passes through the HRSG, ammonia is injected into the exhaust stream. Ammonia reacts with the NOx in the CTG exhaust 10

16 in the presence of the catalyst to produce N 2 gas and water, reducing the NOx emissions from the CTG by as much as 80-90%. Figure 3-1. Tradinghouse process flow diagram from NSR Permit Amendment Application. The catalyst is typically a large ceramic honeycomb with an active catalyst component of a base metal such as vanadium. The catalyst can only operate within a narrow range of temperatures (~ F). When a combined cycle unit starts up, it takes time for the CTG exhaust to become hot enough for the catalyst to operate effectively. Therefore, the NOx emissions are higher during startup than during normal operation. The same is true when the unit is shut down. In both simple cycle and combined cycle operating modes, NOx will be controlled through the use of dry, low-nox combustors in the CTGs. In the combustion of natural gas, NOx is produced by dissociation of N 2 and O 2 at high temperatures. NOx control is achieved by lowering the combustion temperature as much as possible. This is accomplished by ensuring combustion under lean conditions by pre-mixing the air and fuel prior to combustion. The mixing reduces the incidence of fuel-rich pockets that would burn at higher temperatures and the excess air absorbs some of the heat of combustion. 11

17 Two turbine models have been proposed for use at Tradinghouse. General Electric (GE) and Siemens turbines are under consideration by the facility operators. Turbine selection has not yet been determined; therefore two different emissions estimates were made for this project to evaluate the range of potential emissions. The GE Scenario assumes the use of four GE 7FA.05 turbines and the Siemens Scenario assumes the use of four Siemens SGT6-5000f(5)ee turbines, as noted in the Tradinghouse Permit Amendment Application. Figure 3-2. Description of process flow at the Tradinghouse facility EGUs reproduced directly from p. 20 of NSR Permit Amendment Application. Table 3-1 shows emissions of NOx, VOC and CO for the GE and Siemens CTGs under normal operating mode, Siemens fast-ramping mode, and GE peak firing mode. The Siemens fast ramping mode and GE peak firing mode are intermittent operating modes that accommodate limited operation of the turbines in these modes (100 hrs peak firing, 300 hrs ramping), as described in Permit Therefore, these emission rates will only be used for a limited 12

18 number of hours. Startup and shutdown emissions from the CTGs are shown in Table 3-2. Based on the emissions in Table 3-1 and Table 3-2, and information provided in the Tradinghouse Permit Amendment Application on limits on length of time allowed for startup and shutdown, we estimated the magnitude of potential emissions from the Tradinghouse facility during a 24-hour period when the facility is operating for a limited number of hours in either simple cycle mode or combined cycle mode (i.e., the peaking scenario). We assumed that the EGUs are not operating from midnight to 8 am and then undergo an hour-long startup. After an hour of startup, all four EGUs run in normal operating mode with maximum duct firing (combined cycle) or normal operating mode with peak firing/fast ramping (simple cycle) until 9 pm, at which time the EGUs are all shut down. The peaking scenario corresponds to running the units at their maximum short term emissions rates for 12 hours with 1 hour of startup and 1 hour of shutdown and is a hypothetical scenario since the actual operating patterns are not yet known. This scenario was intended to provide a reasonable approximation to the emissions from the Tradinghouse facility for use in the DDM ozone sensitivity modeling and conforms to the information within the Tradinghouse Permit Amendment Application. We calculated the daily total emissions for a single turbine for combined cycle operating mode (lower NOx emissions case) and simple cycle operating mode (higher NOx emissions case) associated with this peaking scenario (Table 3-3 for GE turbine and Table 3-4 for Siemens turbine). Table 3-5 summarizes the maximum emissions from non-ctg emissions sources. Table 3-6 shows hourly emissions from non-turbine equipment sources. Note that the emissions from these sources are the same for operation in simple cycle and combined cycle mode. Table 3-7 shows hourly emissions from all (turbines and non-turbine) Tradinghouse equipment sources for the peaking scenario with all four EGUs operating. Table 3-8 is a summary of the total daily emissions for the peaking operating scenario described above. Daily total NOx emissions when all four EGUs operate in combined cycle were modeled as 0.7 tpd. When all four EGUs operate in simple cycle mode, daily total NOx emissions were modeled as 3.0 tpd. Table 3-1. Tradinghouse turbine maximum hourly emissions in simple and combined cycle modes. 13

19 Table 3-2. Tradinghouse turbine startup and shutdown emissions. Table 3-3. Tradinghouse hourly emissions from a single GE turbine for combined cycle and simple cycle peaking utilization scenarios (lbs). 14

20 Table 3-4. Tradinghouse hourly emissions from a single Siemens turbine for combined cycle and simple cycle peaking utilization scenarios (lbs). 15

21 Table 3-5. Tradinghouse emissions from non-turbine equipment sources. 16

22 Table 3-6. Tradinghouse hourly emissions from non-turbine equipment sources (same emissions for both simple cycle and combined cycle emissions scenarios). 17

23 Table 3-7. Tradinghouse hourly emissions from all (turbines and non-turbine) equipment sources for the peaking utilization scenario. Table 3-8. Tradinghouse peaking utilization scenario emissions summary Lake Creek Power Plant Emissions Scenario Development The process flow diagram for the Lake Creek EGUs is shown in Figure 3-3. Because Lake Creek does not have combined cycle capability, its process flow diagram is simpler than that of Tradinghouse. The Lake Creek process flow is similar to that of Tradinghouse when a Tradinghouse EGU is running in simple cycle mode; CTG exhaust is emitted directly through the simple cycle stack and does not pass through a HRSG/SCR system. The process flow description is summarized in Figure 3-4 in text taken directly from the Lake Creek Permit. 18

24 Figure 3-3. Lake Creek process flow diagram from Lake Creek Permit Figure 3-4. Process flow description from Lake Creek Permit Two turbine models have been proposed for use at Lake Creek. General Electric (GE) and Siemens turbines are under consideration by the facility operators. Turbine selection has not yet been determined; therefore two different emissions estimates were made for this project to evaluate the range of potential emissions. The GE Scenario assumes the use of two GE 7FA.05 turbines and the Siemens Scenario assumes the use of two Siemens SGT6-5000f(5)ee turbines, as noted in the permit. Both turbines will use dry low-nox combustors for NOx emissions control. Table 3-9 shows emissions of NOx, VOC and CO for the GE and Siemens CTGs under normal operating mode, Siemens fast-ramping mode, and GE peak firing mode. The Siemens fast ramping mode and GE peak firing mode are intermittent operating modes that accommodate 19

25 limited operation of the turbines in these modes (100 hrs peak firing, 300 hrs ramping), as described in Permit Therefore, these emission rates will only be used for a limited number of hours. Startup and shutdown emissions from the CTGs are shown in Table Based on the emissions in Table 3-9 and Table 3-10, and information provided in the permit application on limits on length of time allowed for startup and shutdown, we estimated the magnitude of potential emissions from the Lake Creek facility during a 24-hour period when the facility is operating for a limited number of hours in simple cycle mode (i.e., the peaking scenario). We assumed that the EGUs are not operating from midnight to 8 am and then undergo an hour-long startup. After an hour of startup, both EGUs run in normal operating mode with peak firing/fast ramping (simple cycle) until 9 pm, at which time both EGUs are shut down. The peaking scenario corresponds to running the units at their maximum short term emission rates for 12 hours with 1 hour of startup and 1 hour of shutdown and is a hypothetical scenario since the actual operating patterns are not yet known. This scenario was intended to provide a reasonable approximation to the emissions from the Lake Creek facility for use in the DDM ozone sensitivity modeling and conforms to the information within the Lake Creek NSR Permit. We calculated the daily total emissions for a single turbine in simple cycle operating mode under this peaking scenario (Table 3-11 for GE turbine, Table 3-12 for Siemens turbine). Table 3-13 summarizes the maximum emissions from non-ctg emissions sources, and Table 3-14 shows hourly emissions from non-turbine equipment sources. Table 3-15 shows hourly emissions from all (turbines and non-turbine) Lake Creek equipment sources associated with this peaking scenario with both EGUs operating. Table 3-16 summarizes the daily total NOx, VOC and CO emissions in tpd for all Lake Creek emissions sources for the peaking operating scenario described above. Table 3-9. Lake Creek turbine maximum hourly emissions in simple cycle mode. Table Lake Creek turbine startup and shutdown emissions. 20

26 Table Lake Creek hourly emissions from a single GE turbine for the peaking utilization scenario. 21

27 Table Lake Creek hourly emissions from a single Siemens turbine for the peaking utilization scenario. Table Lake Creek emissions from non-turbine equipment sources. 22

28 Table Lake Creek hourly emissions from non-turbine equipment sources. 23

29 Table Lake Creek hourly emissions from all (turbines and non-turbine) equipment sources for the peaking utilization scenario. Table Lake Creek peaking utilization scenario emissions summary. 3.2 Emissions Modeling Once we had developed the emissions estimates shown in Table 3-8 and Table 3-16 we processed the emissions estimates for use in CAMx modeling. In order to model an emissions source within CAMx, it is necessary to define a temporal profile that specifies when the emissions are released during the day. Stack parameters such as stack height and exhaust temperature must be defined and the emissions must be speciated for use in the CAMx chemical mechanism. For the CAMx modeling, we require a temporal profile for distributing Tradinghouse and Lake Creek emissions during the day, but the actual operating patterns of the new EGUs are not yet known and will be determined by future demand for electricity. Therefore, an estimated diurnal 24

30 emissions profile was constructed using emissions from DFW area combustion turbine facilities and one conventional steam generating facility that report emissions to the EPA s Acid Rain Database. The emissions for the facilities were taken from the TCEQ 2012 ozone season day emission inventory. The facilities used were FPLE Forney, LP, Johnson County Generation, Midlothian Energy, and Ray Olinger. For each of the DFW area facilities, the fraction of the daily total NOx emissions emitted during each hour of the day was calculated. A diurnal profile was developed by averaging the hourly fractions over all of the facilities from 2012 DFW area typical ozone season day activity data for CTG facilities (Figure 3-5). The profile reflects a minimum in activity during the early morning hours, with maximum activity during the afternoon, when temperatures are frequently at their highest daily values and demand for electricity is high. Figure 3-5. Temporal allocation of EGU emissions. Vertical axis shows the fraction of daily total emissions that are emitted during each hour of the day. All EPNs (i.e. all emissions sources from Lake Creek and Tradinghouse) were treated as elevated point sources. Stack parameters for Lake Creek and Tradinghouse are shown in Table 3-17 and Table 3-18, respectively. Stack parameters were taken directly from each facility s permit/permit application. Negative numbers in Table 3-17 and Table 3-18 indicate that the emission source was represented as an area source in the permit/application, so a default parameter value for the EPS3 emissions processor (ENVIRON, 2015) was used. The default parameters are: stack height: 3 m, stack diameter: 0.2 m, stack temperature: 294K, and exit velocity: 0.5 m/s. These parameters are intended to simulate a source with low plume rise and exit velocity, which is representative of a non-buoyant area source. For Tradinghouse, we conservatively modeled a single scenario with all four CTGs operating in simple cycle mode, CTG emissions were released through the simple cycle stacks and using simple cycle stack parameters from the Tradinghouse Permit Amendment Application. We did 25

31 not model the combined cycle operations out of the separate combined cycle stacks, as represented in the permit amendment application. The emissions for each EPN were speciated for the CB6r2 chemical mechanism (Yarwood et al., 2012) based on their source classification code (SCC). Default speciation for NOx (denoted profile 0000 in Table 3-19 and Table 3-20 below) was used for the CTGs such that NOx emissions were speciated as 90% NO, and 10% NO 2. Table Tradinghouse stack parameters. Table Lake Creek stack parameters. 26

32 Table Tradinghouse VOC speciation by stack. Table Lake Creek VOC speciation by stack. 27

33 4.0 PHOTOCHEMICAL MODELING 4.1 Modeling Method We estimated potential ozone impacts of emissions from the new EGUs and ancillary facilities at Tradinghouse and Lake Creek using the TCEQ s 2012 NNA ozone modeling platform and the CAMx air quality model s Decoupled Direct Method (DDM) probing tool (Dunker et al., 2002). CAMx is a three-dimensional chemical-transport photochemical grid model and is used for ozone air-quality planning in Texas. The CAMx DDM tool can be used to calculate ozone concentration sensitivity to changes in emissions. In this study, the DDM tool was used to show the sensitivity of ozone in the HOTCOG area to the addition of new NOx emissions at the Tradinghouse and Lake Creek facilities. We computed the sensitivity of the daily maximum 8-hour ozone concentrations (MDA8) to the newly permitted/proposed Tradinghouse and Lake Creek NOx peaking scenario emissions using the CAMx DDM probing tool described in Section 4.2. We focused on the impacts on the MDA8 because the 4 th highest MDA8 in a year is used in the calculation of the design value that is used to determine attainment status of the Waco Mazanec monitor with respect to the ozone NAAQS. The ozone sensitivity was calculated in terms of MDA8 ozone change (ppb) per tpd of NOx emissions from the newly permitted/proposed Tradinghouse and Lake Creek facilities. Because ozone impacts are calculated per unit NOx emissions, and all emissions were modeled out of the simple cycle stacks, the DDM results can be used to estimate ozone impacts from different levels of changes in Tradinghouse/Lake Creek NOx emissions without needing to rerun CAMx. (E.g. DDM results can be used to estimate ozone impacts from either Siemens or GE CTGs, depending on which type of CTG is eventually selected for use at Tradinghouse or Lake Creek). From here, we evaluated ozone impacts due to a series of hypothetical maximum utilization scenarios corresponding to full utilization (24-hours per day) of all CTGs at each facility on a high ozone day with high demand for electricity. We evaluated ozone impacts throughout the modeling domain with a focus on impacts at the Waco Mazanec monitor and the City of Waco. 4.2 CAMx Direct Decoupled Method Probing Tool The DDM probing tool (Dunker et al., 2002) was used to determine ozone impacts of new EGU facilities by calculating the sensitivity of modeled ozone to the new NOx emissions from the peaking utilization scenario. We focused on the sensitivity of ozone to NOx emissions because ozone formation in the HOTCOG area is NOx-limited (McGaughey et al., 2010; 2012; Parker et al., 2013). The CAMx DDM probing tool can calculate the sensitivity of predicted concentrations to pollutant sources (e.g., emissions, initial conditions, boundary conditions) and to chemical rate constants. Sensitivities are calculated explicitly by specialized algorithms implemented in the host CAMx model. 28

34 We define a sensitivity coefficient (s) which represents the change in concentration (c) of a modeled chemical species with respect to some input parameter ( ), evaluated relative to the base state ( = 0 ), c s In general, can be a vector (denoted ), which contains multiple parameters o related to processes in the model (e.g., chemical rate constants) or inputs to the model (e.g., emissions). In this study, c is the ground level ozone concentration (in ppb) and λ corresponds to the peaking utilization scenario NOx emissions (in tpd) from the new EGUs and auxiliary facilities at Tradinghouse and Lake Creek. The base state 0 is the TCEQ 2012 emission inventory that does not contain any emissions from either the new Tradinghouse or Lake Creek facilities. The response of concentration to a change in about the base state 0 can be represented by a Taylor series of sensitivity coefficients: c x, t; c x, t; 0 0 i i n i 1 c i o... ( higher order terms) where n is the number of vector elements, x is the spatial dimension vector, and t is time. If the magnitude of the input perturbation is small, the output response will become dominated by the first-order sensitivity. This is the case in the present study, where the perturbation is the new peaking utilization scenario NOx emissions from Tradinghouse and Lake Creek, which have emissions on the order of 1-3 tpd, while the entire NOx emission inventory for the HOTCOG area is approximately 140 tpd. The increased NOx emissions from either facility represent a perturbation of approximately 2% to the HOTCOG area NOx emission inventory. Therefore it is reasonable to expect that the output ozone response will be linear and dominated by the linear first order sensitivity term. The DDM calculates the first-order sensitivity s i (1) (x,t) with respect to the scalar parameter i. The Taylor series to first order then gives the estimate: c l (1) x, t; c x, t; 0 s x, t... ( higher order terms) i l i i where c l (x;t; i ) is the estimated model result for species l when the perturbed emission inventory (TCEQ base case 2012 inventory + Tradinghouse and Lake Creek emissions) is used as input, and c l (x,t; i =0) is the base case model result when only the base case TCEQ 2012 i 29

35 emission inventory is used as input. The DDM probing tool allows multiple sensitivities to be evaluated in a single CAMx model run and so we evaluated the sensitivity of ozone concentrations to Lake Creek and Tradinghouse individually within the same model run. 4.3 TCEQ 2012 Modeling Platform A June 2012 CAMx modeling database was prepared by the TCEQ for use by the Texas NNAs. The TCEQ prepared meteorological inputs for CAMx, developed emission inventories and made available other inputs such as model boundary conditions. These model inputs were downloaded from the TCEQ s 2012 modeling website 8. The modeling grids are shown in Figure 4-1. CAMx nested 36/12/4 km modeling domains for the 2012 episode. This analysis focused on CAMx model results from the 4 km grid that encompasses East Texas. Figure 4-1. CAMx nested 36/12/4 km modeling domains for the 2012 episode. 4.4 Ozone Modeling Results In this section, we describe the ozone sensitivity to Tradinghouse and Lake Creek EGU NOx emissions calculated using the CAMx DDM probing tool for the peaking utilization scenario. Then we use this ozone sensitivity to determine the ozone impacts of several maximum utilization emissions scenarios. Ozone impacts are evaluated at the Waco Mazanec monitor and across the 4 km modeling domain shown in Figure

36 4.4.1 DDM Ozone Sensitivity Results The DDM ozone sensitivity to NOx emissions for the peaking utilization scenario from Lake Creek and Tradinghouse for grid cells within and near the HOTCOG 6-county area is shown in Figure 4-2. The figure shows the sensitivity (in ppb/tpd) of the episode maximum MDA8 value in each grid cell to the modeled NOx emissions from the new EGUs at the Lake Creek (left panel) and Tradinghouse (right panel) facilities. For both Tradinghouse and Lake Creek, the ozone sensitivity for the month-long modeling episode shows a superposition of plumes emanating from the facility with the direction of the plumes varying according to the winds. The plume directions show that winds during the June 2012 episode were frequently from the northerly clockwise through southerly directions; winds blew from the west relatively infrequently. The ozone sensitivity is similar in magnitude for the two facilities, although the maximum value for the Tradinghouse facility (1.1 ppb/tpd) is slightly higher than that of Lake Creek (0.9 ppb/tpd). The ozone sensitivity is highest near the facilities and reaches its maximum values to the west and southwest of the facilities. This indicates that winds were from the east-northeast on the days when the ozone sensitivity is highest. Figure 4-2. DDM ozone sensitivity (ppb/tpd) of the episode maximum MDA8 ozone to Lake Creek (left panel) and Tradinghouse (right panel) emissions during the June 2012 episode. The HOTCOG counties are outlined in black and the location of the Waco Mazanec (CAMS 1037) monitor is indicated by an open circle. The City of Waco is indicated by a circle with a dot in the middle. The northernmost triangle shows the location of the Tradinghouse facility and the southernmost triangle indicates the Lake Creek facility. HOTCOG s conceptual model of ozone (McGaughey et al. 2010; 2012; Parker et al., 2013), which indicates that high ozone days at the Waco Mazanec monitor occur most frequently when winds are northerly clockwise through southerly. Figure 4-3 shows a wind rose for high ozone days (MDA8 > 75ppb) at the Waco monitor. Wind rose diagrams are used to characterize near-surface wind speeds and directions at a meteorological station. In Figure 4-3, which is 31

37 based on wind data from the Waco Mazanec monitor, winds are binned into speed categories: 0 6 mph, 6 12 mph, mph and > 18 mph. Winds are also binned into direction categories in 22.5 increments with 0 corresponding to north. Each direction category defines a spoke of the wind rose and is defined so that the spoke length is proportional to the number of hours that the wind blows from that direction. The spokes are colored so that each color represents a wind speed and the area of each color is proportional to the amount of time that the wind is blowing at a particular speed from a given direction. Comparison of the wind rose with the plume directions shown indicates that winds during the June 2012 episode are consistent with winds that are typically observed on days with MDA8 > 75 ppb at the Waco monitor. In summary, the plume orientations shown in Figure 4-2 are determined by the June 2012 winds, and although plume impacts could vary for different wind conditions, these winds are generally consistent with winds that occur on high on high ozone days at the Waco Mazanec monitor. Figure 4-3.Wind rose for days when MDA8>75 ppb at the Waco Mazanec (CAMS 1037) monitor Ozone Impact Analysis Once the ozone sensitivity to the new EGU and ancillary facility NOx peaking utilization scenario emissions at Tradinghouse and Lake Creek had been determined, we used the DDM sensitivities shown in Figure 4-2 to calculate ozone impacts (in ppb) under a series of maximum utilization emissions scenarios for each facility. Figure 4-4 shows the calculation method used for the ozone impact analysis. The maximum utilization emissions scenarios were developed by reviewing the Tradinghouse and Lake Creek permit/application documents and determining 32

38 emissions for each facility on an ozone season day when the facilities are utilized for 24-hours per day at their maximum hourly emission rate. For each grid cell, the sensitivity calculated by the DDM probing tool is multiplied by the emissions for a given maximum utilization scenario. Figure 4-4. Ozone impact analysis method Emissions Scenarios Emissions scenarios were developed to evaluate the maximum potential ozone impacts under a maximum utilization operating scenario on an ozone season day when the Tradinghouse and Lake Creek EGUs are utilized at maximum capacity in response to strong demand for electricity. This scenario corresponds to a hot day in the summer months when air conditioner use is high for all hours of the day and night. HOTCOG s conceptual model of ozone indicates that high ozone days (i.e. MDA8 > 75 ppb) at the Waco Mazanec monitor are associated with high temperatures. McGaughey et al. (2012) found that on high ozone days at the Waco monitor from , the daily maximum temperature at the monitor averaged 97 F. On these days, demand for electricity is expected to be strong and so we assumed that all EGUs at Tradinghouse and Lake Creek would be running 24 hours a day. This is a different assumption than was made during the emissions estimation Section 3 to prepare inputs for the DDM modeling, which represented a peaking utilization scenario. Here, we examine a higher NOx emissions scenario that would be possible within the operating restrictions of the Permits/Permit Application Amendment during a multi-day episode of high temperatures in Texas. For Tradinghouse, we estimated the maximum utilization scenario emissions for simple cycle and combined cycle modes. In the first scenario, all four EGUs run 24 hours/day in simple cycle mode and in the second, all four EGUs run 24 hours/day in combined cycle mode. For Lake Creek, both EGUs were assumed to run 24 hours/day in simple cycle mode. The emissions were developed using maximum allowable hourly CTG emissions from Table 3-7 for Tradinghouse and Table 3-15 for Lake Creek. NOx emissions for each maximum utilization emissions scenario are shown in Table 4-1. For Tradinghouse, NOx emissions in the maximum utilization scenario are approximately a factor of 5 higher in the simple cycle case than in the combined cycle case. Note that the emissions in Table 4-1 are within a factor of two of the peaking utilization scenario emissions that were used in the DDM modeling; therefore, we expect the assumption of linearity in model response to these emissions to hold equally well for both sets of emissions. 33

39 Table 4-1. Summary of maximum utilization ozone season day emissions scenarios for Tradinghouse and Lake Creek Ozone Impact Results In this section, we present the ozone impacts calculated for the maximum utilization emissions scenarios summarized in Table 4-1. Figure 4-5 shows the June 2012 episode maximum impact (in ppb) on the MDA8 ozone in each grid cell due to Lake Creek NOx emissions from the maximum utilization scenario. The pattern of impacts is the same as in the ozone sensitivity plot (Figure 4-2) as these ozone impacts were obtained by scaling the Figure 4-2 sensitivities by the maximum utilization scenario emissions. The maximum impact on the MDA8 at the Waco Mazanec monitor location was 1.04 ppb. The maximum impact within the modeling domain was 2.7 ppb and occurred in the immediate vicinity of the Lake Creek plant. Figure 4-5. Episode maximum MDA8 ozone impacts for Lake Creek maximum utilization scenario emissions during the June 2012 episode. SC indicates that the EGUs were assumed to be running in simple cycle (SC) mode. The HOTCOG counties are outlined in black and the location of the Waco Mazanec (CAMS 1037) monitor is indicated by an open circle. The City of Waco is indicated by a circle with a dot in the middle. The northernmost triangle shows the location of the Tradinghouse facility and the southernmost triangle indicates the Lake Creek facility. 34

40 Figure 4-6 shows the June 2012 episode maximum impact (in ppb) on the MDA8 ozone in each grid cell due to Tradinghouse NOx emissions from the maximum utilization scenario. Impacts for the emissions scenario where all EGUs run in combined cycle mode (CC) are shown in the left panel, and impacts for the emissions scenario where all EGUs run in simple cycle mode (SC) are shown in the right panel. For both the simple cycle and combined cycle scenarios, the pattern of impacts is the same as in the ozone sensitivity plot (Figure 4-2), as these ozone impacts were obtained by scaling the Figure 4-2 sensitivities by the maximum utilization scenario emissions. The largest impacts occur in the vicinity of Tradinghouse for both scenarios, but impacts are larger for the simple cycle scenario than for the combined cycle scenario. At the Waco monitor, the episode maximum MDA8 ozone impact was 0.18 ppb for the combined cycle maximum utilization scenario, and 1.06 ppb for the simple cycle maximum utilization scenario. The maximum MDA8 ozone impact at the Waco Mazanec monitor is lower by 0.88 ppb using emissions from Tradinghouse running in combined cycle mode compared to simple cycle mode. Figure 4-6. Episode maximum MDA8 ozone impacts for Tradinghouse maximum utilization scenario emissions during the June 2012 episode. CC indicates that the EGUs were assumed to be running in combined cycle (CC) mode (left panel). SC indicates that the EGUs were assumed to be running in simple cycle (SC) mode (right panel). Otherwise, as in Figure 4-5. We superposed the ozone impacts from Tradinghouse and Lake Creek to estimate the maximum MDA8 ozone impacts when both facilities are operating all EGUs at the maximum utilization emissions rates shown in Table 4-1. We evaluated impacts for the maximum utilization emissions scenario where Tradinghouse EGUs are all operating in simple cycle at the simple cycle emission rates scenario as well as at the combined cycle emission rate scenario. Figure 4-7 shows the maximum MDA8 ozone impacts when both facilities are operating at the maximum utilization emission scenario. The left panel shows the impacts for the scenario when 35

41 all four Tradinghouse CTGs are operating at the combined cycle emission scenario, and the right panel shows the impacts when the Tradinghouse CTGs are operating in simple cycle mode. Ozone impacts are lower when Tradinghouse CTGs run in combined cycle mode compared to simple cycle mode. The maximum combined MDA8 ozone impacts from Tradinghouse and Lake Creek at the Waco Mazanec monitor range from 1.21 ppb for the scenario in which Tradinghouse CTGs are operating in combined cycle mode to 2.04 ppb for the scenario in which Tradinghouse CTGs are operating in simple cycle mode. The maximum combined MDA8 ozone impacts from Tradinghouse and Lake Creek in the vicinity of the City of Waco range from 1-4 ppb depending on whether Tradinghouse CTGs are operating in combined (1 ppb) or simple cycle (4 ppb) mode. Figure 4-7. Episode maximum MDA8 ozone impacts during the June 2012 episode when both Tradinghouse and Lake Creek are operating at the maximum utilization. CC indicates that Tradinghouse EGUs were assumed to be running in combined cycle (CC) mode (left panel). SC indicates that Tradinghouse EGUs were assumed to be running in simple cycle (SC) mode (right panel). Lake Creek EGUs were operating in simple cycle mode in both scenarios. Otherwise, as in Figure 4-5. Figure 4-8 is identical to Figure 4-7, but shows an expanded view of the 4 km modeling domain in order to show impacts beyond the HOTCOG counties. The maximum combined MDA8 ozone impacts from Tradinghouse and Lake Creek operating in the maximum utilization scenario exceeding 1 ppb extend northward into the DFW Nonattainment Area for both cases. For the maximum utilization scenario where Tradinghouse CTGs are operating in simple cycle mode, the combined MDA8 ozone impacts > 2 ppb from Tradinghouse and Lake Creek occur in the 36

42 vicinity of Cleburne (CAMS 77) monitor, and impacts > 3 ppb extend southward into Bell County in the vicinity of the Temple Georgia (CAMS 1045) monitor. Figure 4-8. As in Figure 4-7, with view expanded to show ozone impacts beyond the HOTCOG counties. A summary of the MDA8 ozone impacts at the Waco Mazanec monitor for the maximum utilization emissions scenarios is shown in Table 4-2. Table 4-2. Summary of daily maximum 8-hour average (MDA8) ozone impacts at Waco Mazanec monitor (CAMS 1037) for maximum EGU utilization scenarios. Simple cycle is abbreviated SC and combined cycle is abbreviated CC). Emissions from the permitted/proposed EGUs are predicted to increase ozone in McLennan County. In the June 2012 ozone modeling, NOx emissions from the Tradinghouse maximum utilization emissions scenario had a maximum ozone impact at the Waco monitor of 1.06 ppb when the CTGs were operating in simple cycle mode and 0.18 ppb when the CTGs were operating with combined cycle emissions. For Lake Creek, NOx emissions from the maximum utilization emissions scenario had a maximum ozone impact of 1.04 ppb. The Waco Mazanec (CAMS 1037) monitor ozone impacts for a different time period could be higher or lower, although winds for this episode are consistent with HOTCOG s conceptual 37