# POLK 2-5 COMBINED CYCLE

CONVERSION PROJECT

SUPPLEMENTAL NITROGEN DIOXIDE AIR QUALITY IMPACT ANALYSIS SIMPLE CYCLE UNITS 2 THROUGH 5

Prepared for:

Tampa , Florida

Prepared by:

3701 Northwest 98 th

Street Gainesville, Florida 32606



### ECT No. 110888-02 00

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— 030513 TABLE OF CONTENTS

Section Page

1.0 INTRODUCTION 1

2.0 MODELING PROCEDURES 3

2.1 MODELING APPROACH 3 2.2 MODELS 3 2.3 MODEL OPTIONS: 1

- HOUR AND ANNUAL NO 2 3 2.4 METEOROLOGICAL DATA 4 2.5 BUILDING WAKE EFFECT S 4 2.6 RECEPTOR GRIDS 4 2.7 MODELED EMISSIONS SO URCES

— SCCT UNITS 2 THROUGH 5 4 2.8 MODELED EMISSIONS SO URCES

— OFFSITE SOURCES 5 2.9 BACKGROUND 1

- HOUR NO 2 CONCENTRATION 5

3.0 MODE LING RESULTS 6

3.1 1

- HOUR NO 2 SIL ANALYSIS 6 3.2 ANNUAL NO 2 SIL ANALYSIS 6 3.3 1

- HOUR NO 2 NAAQS ANALYSIS 61 Y: \ GDP

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— 030513 1.0 INTRODUCTION

An applicati on for an air construction/prevention of significant deterioration (PSD) pe rmit for the Tampa Electric Company (Tampa Electric) Polk 2

- 5 Conversion Project (Pr oject) was submitted to the Florida Department of Environmental Protection (FDEP) in
October 2012 . This application included an air quality impact assessment for the four e xisting Polk Power Station (PPS) simple cycle combustion turbine (SCCT) Units 2 through 5 following their conversion to combined cycle mode operation. The dispersion modeling analys is demonstrated that the Project will comply with all applicable ambient air quality
standards.

The Project will be designed to allow the existing combustion turbine generators ( CTGs ) to operate in simple cycle mode when the combined cycle mode steam turb ine generator
is out of service or to meet peak power demands

. For each CTG, a diverter damper in combination with the existing SCCT stack will allow the CTG exhaust gas to bypass the heat recovery steam generator and flow directly to the atmosphere. The P roject also i ncludes the addition of fuel oil

- firing for existing SCCT Units 4 and 5.

As part of its review of the air construction / PSD permit application, FDEP requested a dispersion modeling analysis to assess nitrogen dioxide (NO 2 ) ambient air quality i mpacts for existing SCCT Units 2 through 5 when firing ultra

- low sulfur diesel ( ULSD )
fuel oil. This supplemental air quality analyses to the October 201 2 air constru c tion /PSD permit application provides the additional NO 2 modeling requested by FDEP.

The results of t he SCCT Units 2 through 5 supplemental NO 2 modeling analysis are summarized as follows :

 The h ighest 1

- hour average NO 2 impact is 27.9 micrograms per cubic meter ( μg/m 3 ), which exceed s the 7.5

- μg/ m 3 PSD Class II 1

- hour average NO 2 si gnificant impact level ( SIL )

.

 The maximum annual average NO 2 impact is 0.046 μg/ m 3

, which is below
the 1.0

- μg/ m 3 PSD Class II annual average NO 2 SIL.2 Y: \ GDP

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— 030513  T he cumulative NO 2 model results indicate potential exceedances of the
1

- hour NO 2 national ambient air quality standards ( NAAQS ) . However,
SCCT Units 2 through 5 did not have a significant contribution to any of the
modeled 1

- hour average NO 2 NAAQS exceedances. The maximum SCCT
Units 2 through 5 contribu tion to any poten tial 1

- hour average NO 2 NAAQS
exceedance was 0. 31 μg/ m 3 , well below the 7.5- μg/ m 3 1-hour average NO 2 SIL.

Section 2.0 of th is supplemental report provides the modeling procedures used to assess SCCT Units 2 through 5 1

- hour and annual average NO 2 impacts

. Section 3.0 presents t he results of the modeling analys e s

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— 030513 2.0 MODELING PROCEDURES

2.1 MODELING APPROACH
The supplemental NO 2 dispersion modeling assessment was conducted in accordance with the methodology described in Section 6.0 of the October 2012 air constru c tion /PSD permit application.

2.2 MODELS
The supple mental NO 2 modeling analyses were conducted using the current version of
the U.S. Environmental Protection Agency (EPA)

- approved American Meteorological Society (AMS)/EPA Regulatory Model (AERMOD) modeling system. Specifically,
AERMOD Version 12345 ( Decemb er 11 , 201 2 ) was used

.

2.3 MODEL OPTIONS: 1

- HOUR AND ANNUAL NO 2 Emissions of nitrogen oxides ( NO x ) from combustion sources consist of nitric oxide (NO)
and NO 2 . At stack exit conditions, the primary species is NO, which typically co m prises
90 percent or more of total NO x .

AERMOD includes three options for estimating NO 2 impacts:

 Tier 1

— Assumes complete (i.e., 100

- percent) conversion of NO to NO 2 .

 Tier 2

— Ambient ratio method, which represents the average ambient
NO 2 / NO x ratio. Current EPA guidance recommends using a ratio of 0.80.

 Tier 3

— Uses the ozone limiting method and plume molar volume ra tio
method

.

The Tier 1 option is an AERMOD regulatory default option that may be used without a dditional regulatory agency approval. The Tier 2 option has been historica lly accepted for regulatory modeling applications using an average ambient NO 2 / NO x ratio of 0.75. In a ccordance with EPA’s March 1, 2011, guidance, Tier 2 will be accepted for regulatory modeling applications if the EPA recommended average ambient NO 2 / NO x ratio of 0.80
is used for 1

- hour average NO 2 impacts

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— 030513

For the S C CT Units 2 through 5 1

- hour NO 2 modeling, the Tier 2 approach with an ave rage ambient NO 2 / NO x ratio of 0.80 was used. For annual NO 2 impacts, the Tier 2 a pproach with an average ambient NO 2 / NO x ratio of 0.75 was used. As noted previously
, the approach is a c ceptable without additional regulatory agency approval.

2.4 METEOROLOGICAL DATA The same meteorological data as employed in the prior Polk 2

- 5 Conversion Project modeling (see Section 6.9 of the October 2012 air c onstruction/PSD permit application )
was used for the supplemental NO 2 modeling. This dataset consists of 5 years (i.e., 2006 through 2010 ) of National Weather Service data from the Orlando International Airport

su r face and Tampa Internat ional Airport upper air weather stations.

2.5 BUILDING WAKE EFFECT S The same assessment of building effects as described in Section 6.7 of the October 2012
air construction /PSD permit application was used in the supplemental NO 2 modeling analysis.

2.6 RECEPTOR G RIDS The same receptor grids as described in Section 6.8 of the October 2012 air constru ction /PSD permit application was used in the supplemental NO 2 modeling analysis. The total receptor grid included a total of 1 0,830 individual discrete receptors.

2.7 MODE LED EMISSIONS SOURCES

— SCCT UNITS 2 THROUGH 5
The modeled emissions sources consist ed of the PPS four existing SCCT Units 2 through
5 firing ULSD fuel oil

. SCCT Units 2 through 5 may fire ULSD fuel oil for up to
750 hours per year (hr/yr) under a variety of combustion turbine loads and ambient te mperatures. The SCCTs may also u s e inlet air evaporative cooling. The October 2012 air
construction /PSD permit application identified 11 operating cases for the SCCTs when firing ULSD fuel oil ( reference Table B

- 1 of Appendix B )

. SCCT NO x emissions rates and stack param e ters (i.e., stack exit velocity and temperature) will vary depending on these operating ca s es

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To determine the SCCT operating case that will result in the highest 1

- hour average NO 2 impacts, one inpu t file was created that included each SCCT ULSD fuel oil

- firing case together with the stack parameters and hourly NO x emissions rate for each case. Emi ssions source groups were defined for each of the 11 operating cases. The AERMOD
model was then run usin g this input file together with 5 years of meteorological data and the full receptor grid. Model output consisted of the maximum 1 st highest maximum da i ly
1

- hour results averaged over 5 years.

To determine the SCCT operating case that will result in the h ighest annual average NO 2 impacts, five input files were created (one for each year of meteorological data) that i ncluded each SCCT ULSD fuel oil

- firing case together with the stack parameters and a nnual NO x emissions rate for each case. Model output consi sted of the maximum annual impact for each of the 5 years of meteorological data.

2.8 MODELED EMISSIONS SOURCES

— OFFSITE SOURCES
The same offsite NO 2 emissions inventory as described in Section 6.10.2 of the October
2012 air construction /PSD permit application was used in the supplemental NO 2 mode ling analysis.

2.9 BACKGROUND 1

- HOUR NO 2 CONCENTRATION For the cumulative modeling analysis, total ambient NO 2 impacts consist of the modeled impacts together with a representative background concentration. The same 1

- hou r NO 2 background concentration as described in Section 7.3 of the October 2012 air constru ction /PSD permit application was used in the supplemental NO 2 modeling analysis ; i.e.,
the 3

- year average of the 8 th highest daily maximum ambient air values (69.0 μg/m 3 ) from the Hillsborough County Environmental Protection Commission (HCEPC) monito ring station located at 5121 Grandy Boulevard in Tampa (ID 12

- 057

- 1065) was used as background

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— 030513 3.0 MODELING RESULTS

M odel results for the 1

- hour and annual NO 2 SIL and c umulative NAAQS analys e s are discussed in the following sections.

3.1 1

- HOUR NO 2 SIL ANALYSIS
Table 3

- 1 summarizes t he m aximum 1 st highest maximum daily 1

- hour average NO 2 i mpacts averaged over 5 years for each of the 11 SCCT operat ing cases

. T he highest Tier 2
1

- hour average NO 2 impact of 27.9 μg/m 3 occurred for SCCT ULSD fuel oil

- firing
C ase SC

- 12; i.e., 100

- percent load and 20 degrees Fahrenheit [°F] ambient temperature. Since this impact exceeds the PSD Class II 1

- hour average NO 2 SIL of 7.5 μg/m 3 , cum ulative mo d eling is required to assess total 1

- hour average NO 2 impacts for comparison to
the 1

- hour average NO 2 NAAQS.

3.2 ANNUAL NO 2 SIL ANALYSIS
Table 3

- 2 summarizes the m aximum annual average NO 2 impacts for each SCCT opera ting case and for each of the 5 years of meteorology . The highest annual average NO 2 i mpact of 0.046 μg/m 3 occurred for SCCT ULSD fuel oil

- firing Case SC

- 12 during 2007 year meteorological conditions. Since this impact is below the PSD Class II annual ave rage NO 2 SIL of 1.0 μg/ m 3 , no further modeling is required.

3.3 1

- HOUR NO 2 NAAQS ANALYSIS Cumulative modeling that included SCCT Units 2 through 5, other PPS NO x emissions sources, and the offsite NO x emissions inventory was conducted to obtain 1

- hour NO 2 air quality impacts for th ese emissions sources. The model results were then added to the represent a tive background concentrations to obtain a total impact for comparison to the
1

- hour NO 2 NAAQS. The cumulative modeling was conducted using the full 10,830 individual receptor grids. T able 3

- 3 summarizes t he results of the cumulative
1

- hour a v erage NO 2 mod eling

.

For modeling purposes, t he 1

- hour NO 2 NAAQS is evaluated based on the 5

- year average of the 98 th percentile (i.e., highest, 8 th highest) of the 1

- hour daily maximum NO 2Table 3-1. 1 st Highest Maximum Daily 1-Hour Average NO 2 SIL Impacts—Simple Cycle ULSD Fuel Oil

Number of SCCTs: 4 Tier 2 NO 2 /NO x ratio (1-hour): 0.80

Evaporative Ambient Load Cooling Temperature (%) (Yes/No') (°F) Tier 1 Tier 2

100 No 20 34.9 27.9 75 No 20 33.3 26.7 50 No 20 31.8 25.4 100 No 59 34.3 27.5 100 Yes 59 34.4 27.5 75 No 59 32.1 25.7 50 No 59 31.7 25.3 100 No 90 33.4 26.7 100 Yes 90 33.1 26.5 75 No 90 31.2 25.0 50 No 90 30.8 24.7

Maximums 34.9 27.9

Units Value

— SC-12

2006-2010 μg/m 3 27.9 Annual Impact Location Receptor UTM easting coordinate (X) meters 402,470
Receptor UTM northing coordinate (Y) meters 3,065,883
Receptor elevation meters 41.6 Distance from stack* meters 1,371 Direction vector from stack† degrees 184 PSD SIL μg/m 3 7.5 Exceed SIL Yes/No Yes Percent of SIL % 372.4

*Distance from SCCT Unit 3 stack to the location of highest impact. †Direction from stack toward impact location. For example, 90° means the highest impact is located due east of the SCCT Unit 3 stack.

Source: ECT, 2013. Case Year Tier 2 1-hour NO 2 impact 5-Year Average 2006 through 2010 (μg/m 3 ) Case

Parameter SC-12 SC-13 SC-14 SC-15 SC-16 SC-17 SC-18 SC-19 SC-20 SC-21 SC-22

Y:\GDP-13\TEC\PPS\2-5\SUPNO2MOD-TBL.XLSX\31—3/5/2013Table 3-2. Annual Average NO2SIL Impacts—Simple Cycle ULSD Fuel OilNumber of SCCTs: 4Maximum annual hours: 750 hr/yrTier 2 NO2/NOxratio (annual): 0.75Evaporative AmbientLoad Cooling Temperature(%) (Yes/No) (°F) Tier 1 Tier 2 Tier 1 Tier 2 Tier 1 Tier 2 Tier 1 Tier 2 Tier 1 Tier 2 Tier 1 Tier 2100 N 20 0.043 0.032 0.062 0.046 0.033 0.025 0.043 0.032 0.042 0.032 0.062 0.04675 N 20 0.042 0.031 0.059 0.045 0.033 0.025 0.043 0.032 0.042 0.031 0.059 0.04550 N 20 0.038 0.029 0.053 0.040 0.031 0.023 0.039 0.029 0.038 0.029 0.053 0.040100 N 59 0.042 0.031 0.060 0.045 0.032 0.024 0.042 0.032 0.041 0.031 0.060 0.045100 Y 59 0.042 0.031 0.060 0.045 0.032 0.024 0.042 0.032 0.041 0.031 0.060 0.04575 N 59 0.040 0.030 0.057 0.043 0.032 0.024 0.041 0.031 0.040 0.030 0.057 0.04350 N 59 0.037 0.028 0.052 0.039 0.030 0.023 0.038 0.029 0.037 0.028 0.052 0.039100 N 90 0.040 0.030 0.057 0.043 0.031 0.023 0.041 0.030 0.039 0.030 0.057 0.043100 Y 90 0.040 0.030 0.058 0.043 0.031 0.023 0.041 0.031 0.040 0.030 0.058 0.04375 N 90 0.038 0.029 0.054 0.041 0.031 0.023 0.039 0.029 0.038 0.029 0.054 0.04150 N 90 0.035 0.026 0.049 0.037 0.029 0.022 0.036 0.027 0.035 0.027 0.049 0.0370.043 0.032 0.062 0.046 0.033 0.025 0.043 0.032 0.042 0.032 0.062 0.046Units ValueValueCase — SC-12 PSD SIL 1Year 2007 Exceed SIL NoTier 2 annual NO2impactμg/m30.046Percent of SIL4.6Annual Impact LocationPSDde minimisambient impact 14Receptor UTM easting coordinate (X) meters 400,845 Exceed PSDde minimisambient impact NoReceptor UTM northing coordinate (Y) meters 3,067,301 Percent of PSDde minimisambient impact 0.33Receptor elevation meters 43.2Distance from stack* meters 1,724Direction vector from stack† degrees 272*Distance from SCCT Unit 3 stack to the location of highest impact.†Direction from stack towardimpact location. For example, 90° means the highest impact is located due east of the SCCT Unit 3 stack.Source: ECT, 2013.%Parameter Unitsμg/m3Yes/No%μg/m3Yes/NoSIL Impacts (μg/m3)201020092008200720062006 through 2010SC-21SC-22MaximumsParameterSC-16SC-17SC-18SC-19SC-20SC-12SC-13SC-14SC-15CaseMaximumY:\GDP-13\TEC\PPS\2-5\SUPNO2MOD-TBL.XLSX\32—3/5/2013Table 3-3. 1-Hour NO 2 Cumulative Air Quality Impacts - Simple Cycle ULSD Fuel Oil

Units 2 through 5 Parameter All Sources Contribution

Tier 1 highest 98 th percentile of 1-hour daily maximum NO 2 impacts (μg/m 3 )* 368.9 0.00 413 Tier 2 highest 98 th percentile of 1-hour daily maximum NO 2 impacts (μg/m 3 )† 295.1 0.00 330 Percent of impact (%) 100.0 0.00 11 Receptor UTM easting (meter) 408,028 Receptor UTM northing (meter) 3,071,964 Receptor elevation (meter, amsl) 86.6 Distance from SCCT Unit 3 stack (meter)‡ 7,212 Direction from SCCT Unit 3 stack (degrees)‡ 49

Background 1-hour NO 2 concentration (μg/m 3 ) 69.0
Total 1-hour NO 2 concentration (μg/m 3 ) 364.1

1-hour NO 2 NAAQS (μg/m 3 ) 188 Exceed 1-hour NO 2 NAAQS? (Yes/No) Yes Percent of 1-hour NO 2 NAAQS (%) 193.7

Number of modeled exceedances of the 1-hour NO 2 NAAQS (μg/m 3 )§ 6,963 Number of SCCT Units 2-5 significant impacts to modeled exceedances 0

Highest PPS Units 2-5 Contribution to an Exceedance Total 1-hour NO 2 concentration (μg/m 3 ) 199.0 Receptor UTM easting (meter) 406,028 Receptor UTM northing (meter) 3,057,214 Receptor elevation (meter, amsl) 38.1 Distance from SCCT Unit 3 stack (meter)‡ 10,617 Direction from SCCT Unit 3 stack (degrees)‡ 161 SCCT Units 2 through 5 contribution (μg/m 3 ) 0. 307 SCCT Units 2 through 5 contribution (%) 0.13 1-Hour NO 2 significant impact level (μg/m 3 ) 7.5

*Assumes total conversion of NO x to NO 2 . †Tier 1 impact multiplied by EPA-recommended NO 2 /NO x ratio of 0.80. ‡Distance and direction measured from SC Unit 3 stack located at UTM 402,568 meters easting and 3,067,251 meters northing. §For 5 years including all ranks and background concentrations.

Source: ECT, 2013. 2006 through 2010 5-Year Average Impacts

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impac ts. The AERMOD assessment of SCCT Units 2 through 5 contributions to the
modeled exceedances was conducted by: (a) specifying NO 2 on the AERMOD
COPOLLUTID keyword, (b) selecting 1

- hour averaging using the AVERTIME keyword, and (c) using the MAXDCONT keywo rd with defined source groups of ALL and SC

. The ALL source group includes all (offsite and onsite) modeled emissions sources. SC is
the NO x emissions source code used in AERMOD for SCCT Units 2 through 5 with
Case SC

- 12 emissions rates and stack parameter s.

As shown i n Table 3

- 3 , the model results indicate potential exceedances of the 1

- hour
NO 2 NAAQS. However, SCCT Units 2 through 5 did not have a significant contribution to any of the modeled NO 2 NAAQS exceedances. The maximum SCCT Units 2 through
5 con tribution to any potential 1

- hour average NO 2 NAAQS exceedance was 0. 31 μg/ m 3

, well b e low the 7.5

- μg/ m 3 1

- hour average NO 2 SIL.