Prepared for: City of Palmdale, California



# Class II Area Dispersion Modeling Protocol for the Proposed Palmdale Hybrid Power Project

ENSR Corporation July 2008 Document No.: 10855-002-040C2MPPrepared for: City of Palmdale, California



# Class II Area Dispersion Modeling Protocol for the Proposed Palmdale Hybrid Power Project

_________________________________ Prepared By: Richard P. Hamel

_________________________________ Reviewed By: Brian Stormwind

ENSR Corporation July 2008 Document No.: 10855-002-040C2MPPHPP Appendix G.4, Class II Area Dispersion Modeling Protocol i July 2008 

## Contents

1.0 Introduc tion ................................................................................................................... ..........................1-1

2.0 Dispersion Mode ling Analysis................................................................................................... ...........2-1
2.1 Model Selecti on Crit eria....................................................................................................... ............2-1 2.1.1 Good Engineering Practice St ack Height A nalysis ...........................................................2-1 2.1.2 Dispersion Envi ronment .....................................................................................................2-2 2.1.3 Local Te rrain.................................................................................................................. .....2-2 2.1.4 Representative Meteor ological Da ta .................................................................................2-4
2.2 Dispersion Model Select ion and Applic ation...................................................................................2- 4 2.2.1 Terrain and Receptor Data Processing with AERMAP.....................................................2-6 2.2.2 Meteorological Data Proc essing with AERMET................................................................2-9 2.2.3 Model Op tions .................................................................................................................. 2-14 2.3 Characterization of Sour ces to be Modeled ..................................................................................2-14 2.3.1 Combustion Tu rbines .......................................................................................................2-14 2.3.2 Ancillary Combus tion Unit s ..............................................................................................2-16 2.3.3 Cooling Towe rs................................................................................................................. 2-16 2.3.4 Construction S ources .......................................................................................................2-16
2.4 Evaluation of Air Quality Impacts.............................................................................................. .....2-17 2.4.1 Project Operatio n Impacts................................................................................................2-17 2.4.2 Ambient Background C oncentrati ons.............................................................................. 2-19 2.4.3 NO 2 Modelin g ...................................................................................................................2-2 0

3.0 Additional Imp act Anal yses ..................................................................................................... .............3-1 3.1 Vegetation and So ils ........................................................................................................... .............3-1 3.2 Associated Growth.............................................................................................................. .............3-2

4.0 Refere nces..................................................................................................................... ..........................4-1



## List of Attachments

Attachment 1 AVAQMD Correspondence Relate d to the Cumulative Modeling InventoryPHPP Appendix G.4, Class II Area Dispersion Modeling Protocol ii July 2008 

## List of Tables

Table 2-1 AERSURFACE Season and Bowen Ra tio Condition De signations ......................................2-12 Table 2-2 Ambient Air Impact Criteria ( μ g/m 3 )........................................................................................2-19 Table 2-3 Annual Monitoring Data for Ba ckground Concentra tions ......................................................2-20 Table 3-1 EPA Criteria for Gaseous Pollutant Impac ts on Natural Veget ation and Crops ..................... 3-1



## List of Figures

Figure 2-1 Land-Use and Topography in the Vicinity of the Proposed PHPP Power Bloc k ....................2-3 Figure 2-2 Location of the Palmdale Regi onal Airport Me t Tower ............................................................2-5 Figure 2-3 Near Field Cartesian Receptor Field Used in the PHPP AER MOD Analysis.........................2-7 Figure 2-4 Far Field Cartesian Receptors Field Us ed in the PHPP AER MOD Analys is..........................2-8 Figure 2-5 Aerial Photo of the Area Surrounding the Palmdale Regional Airpor t ..................................2-10 Figure 2-6 1992 NLCD Data Image of the Region Surroundi ng the Palmdale Regi onal Airport...........2-11 Figure 2-7 One km Radius Circle Around the Palmd ale Regional Airport with Surface Roughness Sectors Shown ....................................................................................................2-13 Figure 2-8 Palmdale Regional Airpor t 2002-2004 Wind Rose ................................................................ 2-15 Figure 2-9 Location of Emission Sources Used In Construction Modeling .............................................2-18PHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 1-1 July 2008 

## 1.0 Introduction

The City of Palmdale, California, is proposing to build a hybrid combined-cycle / solar-thermal power plant in the City of Palmdale to the northwest of the Air Force Pl ant 42 / Palmdale Regional Airport. The Project will feature a 2 on 1 combined-cycle configuration with two GE 7FA gas turbines and one steam turbine producing a nominal electrical output of 570 megawatts (MW) along with a 250-acre solar thermal collection field, capable of producing 50 MW. The hybrid power pl ant will be owned by the City of Palmdale and the development managed by Inland Energy and will be known as the Palmdale Hybrid Power Project (PHPP or Project). The combustion turbine trains will include he at recovery steam generator s and will be fueled with natural gas only. In addition to the combustion turb ines, the facility will contain ancillary combustion equipment including a natural gas-fired auxiliary boiler, a natural gas-fired heat transfer fluid (HTF) heater, a diesel-fired emergency generator, and a diesel-fired fire water pump engine. The facility will also include a wet mechanical draft cooling tower.
The proposed facility will be located in an area th at is designated federal non-attainment for respirable particulate matter (PM10) and ozone (O 3 ), and attainment or unclassified for sulfur dioxide (SO 2 ), nitrogen dioxide (NO 2 ), carbon monoxide (CO), and fine particulate matter (PM2.5). Based on an estimate of preliminary facility air emissions, the Project will be a major source with respect to New Source Review (NSR) regulations, will trigge r Prevention Significant Deterioration (PSD) review for NO 2 , CO, PM10, and PM2.5 and will be subject to non-at tainment new source review (NAN SR) for PM10 and ozone precursors NO X and volatile organic compounds (VOC). The facility will be a minor source of SOx, lead, and other PSD pollutants. Therefore, as required by the PSD regula tions, Inland Energy will conduct a Best Available Control Technology (BACT) evaluation to determine the bes t level of control for CO, taking into account the environmental, economic and energy consumption impacts. Per NANSR, a Lowest Achievable Emission Rate (LAER) review for NO X (as an ozone precursor) and PM10/PM2 .5 will be conducted. The U.S. Environmental Protection Agency (EPA) administers the PSD program in this area and the Antelope Valley Air Quality Management District (AVAQMD ) manages the local NANSR program.
Air quality modeling will be performed in accordanc e with EPA modeling guidelines (EPA, 2005) for all sources and will be conducted with the EPA’s AERMOD dispersion model to demonstrate compliance with the National Ambient Air Quality Standards (NAAQS), California Ambient Air Quality Standards (CAAQS) and Prevention Significant Deterioration (PSD) increments in the local (Class II) area.
Dispersion modeling will also be conduc ted to assess potential impacts at Class I Areas in accordance with PSD modeling requirements. The details of t he proposed modeling approach for Class I Areas is documented in a separate modeling protocol. This Cla ss II Area modeling protocol also does not address the procedures or methodology that will be used in eval uating potential health risks from air toxics emissions. The proposed approach for conducting a health risk assessment (HRA) will be provided in the Application for Certification (AFC).PHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-1 July 2008 

## 2.0 Dispersion Modeling Analysis

This section presents the modeling analysis that will be conducted to assess am bient air quality impacts which will ultimately demonstrate compliance with applicable State and Federal ambient air quality standards. The analyses will be conducted in accordanc e with the EPA Guideline on Air Quality Models (GAQM; as incorporated in Appendix W of 40 CFR Part 51 Revised November 9, 2005). The revised version of GAQM adopts AERMOD as a preferred gen eral purpose dispersion model for both flat and complex terrain.


### 2.1 Model Selection Criteria The suitability of an air quality dispersion model for a particular application is dependent upon several factors. For this study, the following selection criteria have been evaluated:

• Stack heights relative to nearby buildings/structures;

• Dispersion environment;

• Local terrain; and

• Availability of represent ative meteorological data.


### 2.1.1 Good Engineering Practice Stack Height Analysis The EPA modeling guidelines require the evaluation of the potential for physical st ructures to affect the dispersion of emissions from stack sources. The ex haust from stacks that are located within specified distances of buildings, and whose physical heights are below specified levels, may be subject to “aerodynamic building downwash” under certain meteorologi cal conditions. If this is the case, a model capable of simulating this effect must be employed.
The analysis used to evaluate the potential for build ing downwash is referred to as a Good Engineering Practice (GEP) stack height analysis. Stacks with hei ghts below physical GEP are considered to be subject to building downwash. In the absence of structural effects, EPA has established a default GEP height of 213 feet (65 meters). Any portion of a stack above the maximum of the physic al or default GEP height cannot be used in the dispersion m odeling analysis for purposes of com parison to ambient impact criteria.
A GEP stack height analysis will be performed for the proposed ancillary equipment stacks in accordance with EPA’s GEP stack height guidelines (EPA, 1985). Per the guidelines, the physical GEP height, H GEP , is determined from the dimensions of all buildings which are within the region of influence using the following equation:

H GEP = H B + 1.5L
Where: H B = height of the structure within 5L of the stack which maximizes H GEP , and L = lesser dimension (height or projected width) of the structure.
For a squat structure, i.e., height less than projected width, the formula reduces to:
H GEP = 2.5H B In the absence of influencing structures, a default G EP stack height is credited up to 213 feet (65 m).
The GEP stack height for all proposed stacks will be determined using the EPA Building Profile Input Program (BPIP) that performs the GE P calculation for a multi-building complex on a stack-by-stack basis.PHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-2 July 2008 The stack heights of the ancillary equipment have not been determined at this time but it is anticipated that these stacks will be less than their respective GEP fo rmula heights and, therefore, subject to building downwash. Therefore, build ing dimensions developed by BPIP for all stacks will be input to the dispersion model as necessary.
The results of the GEP analysis will be documented in the AFC and the BPIP input and output files will be provided in the modeling archive s ubmitted with the AFC (Appendix G.6).


### 2.1.2 Dispersion Environment The application of the dispersion model requires characterization of the local dispersion environment (within three kilometers [km]) as either urban or rural, based on an EP A-recommended procedure (Auer, 1978) that characterizes an area by prevalent land use. This land use approach classifies an area according to 12 land use types. In this scheme, areas of industria l, commercial, and compact residential land use are designated urban. According to the GAQM, if more than 50 percent of an area within a three-km radius of the proposed facility is classified as rural, then rura l dispersion assumptions are to be used in the dispersion modeling analysis. Conversely, if more than 50 percent of the area is urban, urban dispersion is assumed.
As shown in Figure 2-1, the land-use within three km of the proposed facili ty is characterized as rural based on the EPA-recommended procedure. AERMOD does not r equire any specification for rural applications since rural dispersion is the default dispersion mode.



### 2.1.3 Local Terrain The EPA modeling guidelines require that the differ ences in terrain elevations between the stack base and model receptor locations be considered in the mode ling analyses. For dispersi on modeling purposes, there are three types of terrain:

• Simple terrain – locations where the terrain elevation is at or below the exhaust height of the stacks to be modeled;

• Intermediate terrain – locations where the terrain is between the top of the stack and the modeled exhaust “plume” centerline (this varies as a function of plume rise, which in turn, varies as a function of meteorological condition); and

• Complex terrain – locations where the terrain is above the plume centerline.
Prior to the introduction of AERMOD, these terrain type s had to be modeled in different ways that were not necessarily consistent. One advantage of using AE RMOD is that there is a seamless and consistent approach to all terrain types.
The terrain immediately surrounding the proposed site lo cation is primarily flat, desert scrubland. The terrain to the south and west of the Project site is mountainous with elevations exceeding 4,500 feet (compared to the Project base elevation of 2,513 feet ). The terrain gradually slopes upward to the south and west for the first 10 kilometers away from the Pr oject then rapidly rises to elevations in the 3,000-4,000 foot range.PHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-3 July 2008 Figure 2-1 Land-Use and Topography in the Vicinity of the Proposed PHPP Power BlockPHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-4 July 2008 

### 2.1.4 Representative Meteorological Data The Project modeling will use a thr ee-year sequential hourly meteorologi cal data set, consistent with Appendix B of the California Energy Commission’s Ru les of Practice and Procedure & Power Plant Site Certification Regulations (2000). Three years (2002-2004) of surface meteorological data are available from the Automatic Surface Observing System (ASOS) tower at nearby Palmdale Regional Airport and are proposed for this application. Per discussion with Brett Banks of the Antelope Valley Air Quality Management District (AVAQMD), this was the preferred opt ion if the data were available. A review of the completeness of the data at Palmdale Regional Airport showed that the data capture was slightly below the 90% completeness per quarter for all required data types recommended in the Meteorological Monitoring Guidance for Regulatory Modeling Applicati ons (EPA, 2000) for the following quarters:
2002: Q1 Wind direction 86.5% complete 2002: Q2 Wind direction 89.1% complete 2003: Q3 Wind direction 83.3% complete
All other quarterly values exceeded the recommended 90% th reshold. Two other sources of meteorological data were considered as alternativ es: The Lancaster Division Street Met Tower in Lancaster, CA, and William J. Fox Field north of Lancaster. A data comple teness study of these two locations revealed that the data capture at each was lower than that of Palmdal e Regional Airport. Palmdale Regional Airport is therefore the best option for this analys is because of a) superior data captur e, b) it’s close proximity to the Project site (the met tower is less than 2 miles from the proposed turbine stack locations) c) the similarity in surface characteristics between the airport and the Pr oject site, and d) AVAQMD ’s preference to use the Palmdale Regional Airport Data.
The location of the Palmdale Regional Airport relative to the proposed Project location is shown in Figure 2-2. The anemometer height at Palmdale Regional Airport is 10 meters. Concurrent upper air data from Mercury Desert Rock Airport in Mercury, Nevada will also be used as required for the dispersion modeling. Use of 2005, 2006, and 2007 data is not proposed because of the poor data recovery of the upper air data at Mercury Desert Rock Airport during these years. Su rface data will be acquired from Trinity Consultants, Inc., filled per the Procedures for Substituting Values for Missing NWS Meteorological Data for Use in Regulatory Air Quality Models memo by Atkins on and Lee (EPA, 1992). The upper air data will be downloaded from the NCDC RAOB Database website ( http://raob.fsl.noaa.gov/ ). 

### 2.2 Dispersion Model Selection and Application The EPA GAQM prescribes a set of approved models fo r regulatory applications for a wide range of source types and dispersion environments. Based on a revi ew of the factors discussed above, the AERMOD model is proposed to assess air quality impacts for th e Project. AERMOD is a state-of-the-art dispersion model that incorporates modeling improvements espec ially for applications involving building downwash and complex terrain. AERMOD has become the recommended model by the EPA for general use to replace the Industrial Source Complex - Short Term 3 model. The latest version of AERMOD (07026), the AERMET (06341) meteorological preprocessor, and the AERMAP (06341) terrain preprocessor will be used in this application.
AERMOD will be applied with the three years of me teorological data discussed above for all receptors (simple and complex terrain) in the modeling domain (see Section 2.3.1) to assess air quality impacts from the Project. AERMO D will be applied to assess the maximu m criteria pollutant concentrations including 1-hour and annual NO 2 , 24-hour and annual PM10/PM2.5, 1-hour and 8-hour CO, and 1-hour, 3-hour, 24-hour and annual SO 2 . The proposed meteorological data processing with AERMET and development of the receptor grid with AERMAP are discussed below.PHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-5 July 2008 Figure 2-2 Location of the Palmdale Regional Airport Met TowerPHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-6 July 2008 

### 2.2.1 Terrain and Receptor Data Processing with AERMAP A comprehensive Cartesian receptor grid extending to 20 km from the center of t he power block will be used in the AERMOD modeling to assess maximum ground-leve l pollutant concentrations. Based on preliminary modeling, the 20-km receptor grid will be sufficien t to resolve the maximum impacts and any significant impact area(s).
The Cartesian receptor grid will consis t of the following receptor spacing:

• Fenceline to 3,000 meters at 100 meter increments

• Beyond 3,000 meters to 5,000 meters at 200 meter increments

• Beyond 5 kilometers to 10 kilometers at 500 meter increments

• Beyond 10 kilometers to 20 kilometers meters at 1,000 meter increments
Discrete receptors will be placed approximately every 50 meters along the Project fence line for increased resolution of impacts along this boundary.
The AERMAP receptor locations and the proposed AERM AP domain are shown in Figure 2-3 (near-field portion of the receptor grid) and Figure 2-4 (far-field receptors and AERMAP domain). An additional five km was added to the AERMAP domain beyond the 20 km receptor grid shown in Figure 2-4. This additional area is included in order to provide sufficient resolution of the hill height scale required for each receptor. Terrain elevations from Digital Elevation Model (DEM ) data acquired from United States Geological Service (USGS) will be processed with AER MAP to develop the receptor terra in elevations and corresponding hill height scale required by AERMOD. Al l of the DEM files will be from Un iversal Transverse Mercator (UTM) Zone 11 and referenced to North American Datum (NAD) 27 (Note that the receptors shown in Figures 2-3 and 2-4 are referenced to NAD27). The DEM files will al so be included in the modeling archive that will be submitted along with the AFC.PHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-7 July 2008 Figure 2-3 Near Field Cartesian Receptor Field Used in the PHPP AERMOD AnalysisPHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-8 July 2008 Figure 2-4 Far Field Cartesian Receptors Field Used in the PHPP AERMOD AnalysisPHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-9 July 2008 

### 2.2.2 Meteorological Data Processing with AERMET Three years (2002-2004) of surface observations from the NWS tower at Palmdale Regional Airport in Palmdale, and concurrent upper air data from Mercury Desert Rock Airport in Mercury will be processed with AERMET, the meteorological preprocessor for AERMOD.
AERMET will be applied to create two meteorologica l data files required for input to AERMOD:

Surface : A file with boundary layer parameters such as sensible heat flux, surface friction velocity, convective velocity scale, ve rtical potential temperature gradient in the 500-meter layer above the planetary boundary layer, and convective and mechanical mixing heights. Also provided are values of Monin-Obukhov le ngth, surface roughness, albedo, Bowen ratio, wind speed, wind direction, temperature, and he ights at which measurements were taken.

Profile : A file containing multi-level meteorologica l data with wind speed, wind direction, temperature, sigma-theta ( σ θ ) and sigma-w ( σ w ) when such data are available. For this application involving the Lancaster tower data, t he profile file will contain a single level of wind data (9.3 meters) and the temperature data only.
AERMET requires specificatio n of site characteristics including surface roughness (z o ), albedo (r), and Bowen ratio (B o ). These parameters were developed according to the guidance provided by EPA in the recently revised AERMOD Implementation Guide (AIG) (EPA, 2008a).
The revised AIG provides the following recommendatio ns for determining the site characteristics:
1. The determination of the surface roughness length should be based on an inverse distance weighted geometric mean for a default upwind distance of one km relative to the measurement site. Surface roughness length may be varied by sector to account for variations in land cover near the measurement site; however, the sector widths s hould be no smaller than 30 degrees. As discussed further below, three sectors were used in this application. 2. The determination of the Bowen ratio will be bas ed on a simple unweighted geometric mean (i.e., no direction or distance dependency) for a representat ive domain, with a default domain defined by a 10 km by 10 km region cent ered on the measurement site. 3. The determination of the albedo should be based on a simple unweighted arithmetic mean (i.e., no direction or distance dependency) for the same repr esentative domain as defined for Bowen ratio, with a default domain defined by a 10 km by 10 km region centered on the measurement site.

The AIG recommends that the surface characteristi cs be determined based on digitized land cover data. EPA has developed the AERSURFACE tool that will be used to determine the site characteristics based on digitized land cover data in accordance with the recommendations from the AIG discussed above. AERSURFACE incorporates look-up tabl es of representative surface char acteristic values by land cover category and seasonal category. AERS URFACE will be applied with the instructions provided in the AERSURFACE User’s Guide (EPA, 2008b).
The current version of AERSURFACE (Version 08009) suppor ts the use of land cover data from the USGS National Land Cover Data 1992 archives (NLCD92) ( http://edcftp.cr.usgs.gov/ pub/data/landcover/states/ ). The NLCD92 archive provides data at a spatial resoluti on of 30 meter based on a 21-category classification scheme applied over the continental U.S.PHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-10 July 2008 Figure 2-5 Aerial Photo of the Area Surrounding the Palmdale Regional AirportPHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-11 July 2008 Figure 2-6 1992 NLCD Data Image of the Region Surrounding the Palmdale Regional AirportPHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-12 July 2008 Visual inspection of recent satellite images (2005) in the area of the measurement site (see Figure 2-6), compared to the 1992 1 land cover images (Figure 2-7) indicate that there have been no significant changes in land use cover confirming the use of the 1992 data will be reasonable. As recommended in the AIG for surface roughness, the one kilometer area was broken down into sectors for the analysis. Two sectors were identified for this analysis based upon visual observation of the land-us e around the monitoring station as shown on aerial photographs (see Figure 2-7).
In AERSURFACE, the various land cover categories are linke d to a set of seasonal surface characteristics. As such, AERSURFACE requires specification of the s easonal category for each month of the year. The following five seasonal categories are offered by AERSURFACE:
1. Midsummer with lush vegetation; 2. Autumn with unharvested cropland; 3. Late autumn after frost and har vest, or winter with no snow; 4. Winter with continuous snow on ground; and 5. Transitional spring with partial green coverage or short annuals.
The designations used in this applicat ion are summarized in Table 2-1.
Table 2-1 AERSURFACE Season and Bowen Ratio Condition Designations
Season Bowen Ratio Category Month 2002-2004 2002 2003 2004 January Winter * Dry Dry Dry February Winter * Dry Dry Wet

March Autumn Dry Wet Average April Autumn Average Wet Average May Summer Average Wet Average June Summer Average Average Average July Summer Average Wet Average August Summer Aver age Average Average September Summer Average Average Average

October Summer Average Average Wet November Autumn Average Average Wet December Autumn Wet Average Wet * The “Late autumn after frost and harvest or winter with no snow” category will be used for January and

February season.

1 1992 is the data set that the EPA uses for AERSURFACE. This data set is reviewed to verify that the area hasn’t

significantly changed over time. Aerial photos of this Palmdale area show that there has been no major development in this period.PHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-13 July 2008 Figure 2-7 One km Radius Circle Around the Palmdale Regional Airport with Surface Roughness Sectors ShownPHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-14 July 2008 In addition, for Bowen ratio, the land use values are linked to three categories of surface moisture corresponding to average, wet and dry conditions. The surface moisture condition for the site may vary depending on the meteorological data period for which the surface characteristics will be applied. AERSURFACE applies the surface moisture condition for th e entire data period. Therefore, if the surface moisture condition varies significantly across the da ta period, then AERSURFACE can be applied multiple times to account for those variations. As recomm ended in the AERSURFACE User’s Guide, the surface moisture condition for each month will be determined by comparing precipitation for the period of data to be processed to the 30-year climatological record, select ing “wet” conditions if prec ipitation was in the upper 30th-percentile, “dry” conditions if pr ecipitation was in the lower 30th-per centile, and “average” conditions if precipitation was in the middle 40th-percentile. The monthly designations of su rface moisture input to AERSURFACE are also summarized in Table 2-1.
The base elevation used for the Palmdale Regional Ai rport will be 769.3 meters (2,524 feet) above sea level. A three-year wind rose is provided as Figure 2-8.


### 2.2.3 Model Options AERMOD will be applied with the EPA recommended default op tions. Model iterations will be conducted for each year of meteorological data to identify the ma ximum impacts over all three years for the pertinent averaging periods.


### 2.3 Characterization of Sources to be Modeled The Project will include the following air emission sour ces that will be included in the modeling analysis:

• Two combined cycle combustion turbines, each with heat recovery steam generators (HRSGs)

• Auxiliary boiler

• Emergency generator engine

• Fire-water pump engine

• Heat transfer fluid heater

• Cooling tower
A preliminary plot plan of this equi pment is shown in Figure 2-9. Ca lculation of emissions, including proposed control technology, will be provided in the AFC, PSD and NANSR permit applications.



### 2.3.1 Combustion Turbines

2.3.1.1 Normal Turbine Operations The dispersion modeling analysis wi ll be conducted with emission rates and flue gas exhaust characteristics (flow rate and temperature) that are expected to repr esent the range of possible values for the natural gasfired turbines under consideration. Because turbine emission rates and flue gas characteristics for a given turbine load vary as a function of ambient temperat ure and operational load, data will be derived for three ambient temperatures for natural gas fuel at each of the three operati ng load points (100%, 75% and 50%). The temperatures will cover a representative min imum, annual average and a representative maximum. The 100% load case will also include maximum duct fi ring of the HRSGs. Although maximum emissions will occur during 100% load operation, plume rise will be lower and hence impacts could be greater during partial load conditions. Therefore, modeling will be conducted for all cases to define the worst-case scenario for each pollutant.PHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-15 July 2008 Figure 2-8 Palmdale Regional Airport 2002-2004 Wind RosePHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-16 July 2008 2.3.1.2 Startup/Shutdown Turbine Operations During startup and shutdown of the combustion turbines, emissions of NO X and CO will be higher than normal operations. As such, worst-case startup and sh utdown conditions will be modeled with AERMOD for comparison to the 1-hour NO 2 CAAQS of 339 μg/m 3 and the 1-hour CO CAAQS of 23,000 μg/m 3 . An analysis of maximum 8-hour CO impacts for com parison to the CAAQS of 10,000 μg/m3, including startup/shutdown, will also be conducted. Stack parameters and emissions data required for modeling short-term startup/shutdown scenarios will be provided in the modeling repor t. It is anticipated that stack parameters corresponding to a 20 percent load will be used as representative of this operating mode. If required, application of the ozone limiting method (O LM) as described in Section 2.4.3 will be used to account for the oxidizing potentia l of background ozone to convert NO X to NO 2 on an hourly basis. Startup and shutdown emissions will be accounted for in th e annual average modeling by developing scenarios, such as base load and daily cycling cases, to determine the worst case emissions. To assess annual average impacts, the maximum annual potential emis sions will be modeled with 100% load stack parameters and annual average temperature as this ca se will be most representative of annual average conditions.
2.3.1.3 Turbine Commissioning Maximum emissions during the initial tuning and test ing of the combustion turbines at the end of construction of the power pl ant will be similar to emissions during st artup and shutdown operations. To the extent where there are differenc es, short-term modeling of NO X and CO emissions will also be performed to determine impacts fr om this phase.


### 2.3.2 Ancillary Combustion Units The Project will include an auxilia ry boiler, emergency generator engine, fire-water pump engine and heat transfer fluid heater. These units will each have a dedi cated stack. The modeling of these sources will be based on maximum (short-term and annual) emissions of the criteria pollutants and appropriate stack parameters based on the size of the units proposed. The stack parameters and air emissions of all the units will be documented within the modeling report.


### 2.3.3 Cooling Towers The Project will include a wet mechanical draft coolin g tower. Drift eliminators will be utilized to minimize cooling tower drift. Cooling tower drift consists of water droplets containing dissolved solids which are entrained in the airflow through the tower and carried out to the atmosphere. As su ch, the cooling tower will be a source of particulate matter emissions and will be included in the modeling analysis to assess Project PM10/PM2.5 air quality impacts.
The PHPP cooling tower will consist of 10 cells. Each cell will be modeled as an individual point source. The modeling report will document the source paramet ers including the fan stack height, inside diameter, exhaust temperature and velocity.


### 2.3.4 Construction Sources Construction of the PHPP is anticipated to take 27 months. Construction-related air emissions will include exhaust and fugitive dust from vehicl e and construction equipment and windblown fugitive dust from grading and other soil disturbing activities. Criteria pollutant emissions will be modeled to determine maximum air quality impacts. Modeling will reflect that constructi on will primarily occur during daylight hours. The maximum modeled concentrations wi ll then be added to background concentrations and compared to the applicable standards.PHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-17 July 2008 Construction-related emissions will be modeled using the AERMOD model (version 07026). Emissions of criteria pollutants for the construction sources will be modeled as layered area sources, with one layered area source representing power block construction, and another representing solar array construction. Buoyancy and mechanical turbulence from the hot exhaus t and mobility of the c onstruction equipment will be included as an initial vertical dimension in the area source algorithm. Fugiti ve dust emissions and onsite motor vehicles will be modeled as a separate low-leve l area source since these emissions would almost all occur near ground level.
For the emission source associated with the power block construction, an area polygon source with a total area of about 95,260 square meters (m 2 ) will be used. This area represents the size of the power block and will be used to compute the emission flux for the power block area. For the construction sources associated with the solar array construction, a rectangular area source with an area of about 100,700 m 2 will be used. The solar array area source represents the largest area that is expected to be under construction at a given time and the solar array construction emission flux wi ll be calculated based on this area. The power block sources will be located over the proposed footprint for the power block equipment, while the solar array construction sources will be placed just to the west of the power block to allow for potential interaction of plumes from both area sources. Each of these locations, shown in Figure 2-9, will have two overlaid area sources, one for the windblown fugitive and on-site vehicle emissions, and a second for the construction equipment with vertical exhaust pipes.
A release height of 2.0 meters will be assumed for the fugitive / onsite vehicles sources, with an initial plume height of 15 feet (4.57 m). Following EPA AERMOD gu idance (EPA, 2004), the initia l area source vertical standard deviation for construction co mbustion emissions is estimated as the plume depth divided by 2.15, or 2.13 m.
The large construction equipment will be assumed to ha ve a release height of 3.7 m. The initial vertical depth of the diesel exhaust plume for construction activi ties will be estimated as four times the release (exhaust) height. This height (14.8 m) takes into account the plume rise of the hot diesel exhaust, mechanical mixing on the site introduced by the movement of heavy equipment, and structure wake turbulence introduced by buildings and structures on t he Project site. The initial area source vertical standard deviation for the construction equipment is calculated by taking th is vertical depth and dividing by 2.15 for an initial sigma-z of 6.88 meters.


### 2.4 Evaluation of Ai r Quality Impacts 2.4.1 Project Operation Impacts The modeling of normal plant operations using AERMOD will be done as a multi-step process. First, the worst-case impacts for the combustion turbines (bas ed on different load and temperature profiles) will be identified. Next, the worst-case combustion turbine im pacts will be combined with normal operations of the other facility sources. The maximum air quality impac ts due to emissions from th e Project sources will be compared to the EPA Significant Impact Levels (SILs) (s ee Table 2-2). For criteria pollutants and averaging periods where the modeled Project impacts are below their respective SILs, no further analysis will be required to demonstrate compliance with the PSD incr ements. For pollutants and averaging periods where modeled impacts are greater than the SILs, multi-s ource modeling will be required to determine the cumulative impacts of the Projec t and nearby major background sources to demonstrate compliance with the PSD increments. In addition, the CEC requires a cumulative analysis to demonstrate compliance with the NAAQS/CAAQS.
ENSR submitted a letter to the AVAQMD on July 2, 20 08 requesting a background inventory for sources to be included in the cumulative modeling. ENSR was contacted by Chris Anderson and recommended that two facilities close to the Projec t site, Lockheed-Martin Aeronautics and Northrop-Grumman Corporation, be included in the cumulative analysis.PHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-18 July 2008 Figure 2-9 Location of Emission Sources Used In Construction ModelingPHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-19 July 2008 Table 2-2 Ambient Air Impact Criteria ( μ g/m 3 )

NAAQS Pollutant Averaging Period PSD Class II Significant Impact Levels PSD Class II Increments CAAQS Primary Secondary
1-hour -- -- 339 1 -- -- NO 2 Annual 1 25 57 100 100 1-hour 2,000 -- 23, 000 40, 000 NA CO 8-hour 500 -- 10, 000 10, 000 NA 24-hour 5 30 50 150 150 PM10 Annual 1 17 20 -- -- 24-hour -- -- -- 35 35 PM2.5 Annual -- -- 12 15 15 1-hour -- -- 655 -- -- 3-hour 25 512 -- NA 1300 24-hour 5 91 105 365 NA SO 2

Annual 1 20 -- 80 NA

1 The California Office of Administrative Law (OAL) approved the rulemaking on February 19, 2008, and the revised

NO 2 standard became March 20, 2008.

The cumulative source database was received in the form of a Hotspots Analysis and Recording Program (HARP) modeling file for the two facilities which included the sources the be modeled and included the necessary stack parameters and emissions data.
The HARP data included 284 sources (129 at Lockheed, 155 at Northrop), the vast majority of which had very small emissions. Because of the large number of sources, AERMOD runs would take an extremely long time to complete. Therefore, following consul tation with the AVAQMD, it was determined that the modeling would only explicitly include the sources that e mit 5% or greater of the total facility emissions for each pollutant. The emissions from sources not modeled (i.e., sources wi th emissions less than 5% of the total) will be added to the highest emit ting source for that pollutant. In the case where there are multiple sources with the highest emission rate, the emissions from sources not modeled will be added to the with source closest to the Projec t site. This approach will provide a reasonable simplifica tion to the modeling that will result in more manageable modeling run times while ensuring that the emissions from the non-Project facilities are properly accounted fo r in the cumulative modeling.
The correspondence related to the cumulative inventory is contained in Attachment 1 to this protocol..


### 2.4.2 Ambient Background Concentrations An ambient regional background component repres enting non-modeled source contributions will be added to the modeled concentrations to demonstrate compliance with the CAAQS/NAAQS. Regional background concentrations from available ambient moni toring data most representative of current air quality in the proposed project impact area are shown in Table 2-3. These data represent the three most recent years (2005-2007) available from the Lancaster Division Street monitor (same location as the meteorological data), except for the SO 2 background data, which represents the three most recent years (2005-2007) available from the Burbank We st Palm Avenue monitor in Burbank, CA.PHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 2-20 July 2008 Table 2-3 Annual Monitoring Data for Background Concentrations
Maximum Observed Concentrations (μg/m 3 ) Pollutant Period 2005 2006 2007
1-hour 139.2 124.1 120.4 NO 2 Annual 28.2 28.2 26.3
1-hour 3,335 3,680 2,875 CO 8-hour 1,725 1,840 1,495
24-hour 55 65 86 PM10 Annual 22 23 25
24-hour 16 13 20 PM2.5 Annual 8.9 7.4 8.0
1-hour 34.1 23.6 21.0
3-hour 23.6 13.1 13.1
24-hour 15.7 10.5 7.9 SO 2

Annual 5.2 2.6 2.6 All short term values are the maximum concentration with the exception of PM2.5 which is the 98 th percentile. Annual values are mean annual concentrations.



### 2.4.3 NO 2 

### Modeling To complete the Ambient Air Qualit y Impacts Analysis (AQIA) for NO 2 , the modeled ground-level concentrations resulting from NO X emissions must be converted to NO 2 . For the PHPP AQIA, initially the EPA national default conversion factor of 75 percent will be applied to the modeled NO X concentrations to estimate NO 2 . If further refinement of the NO 2 concentrations is necessary, the ozone limiting method (OLM) will be applied as implemented in AERMOD with the use of hourly ozone concentrations from the most representative monitor. In usi ng the OLM in AERMOD, conversion of NO X emissions to NO 2 concentrations are limited based on the availability of ozone as determined by the ambient background levels. If necessary, background ozone levels will be obtained from the EPA AirData website for the Lancaster monitoring station.PHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 3-1 July 2008 

## 3.0 Additional Impact Analyses

PSD regulations require a review of the following addi tional potential impacts which may result from the proposed project with respect to the following:

• Vegetation and Soils

• Associated Growth

• PSD Class I Area Impacts
Potential impacts to PSD Class I Areas are addressed in a separate modeling protocol. 

### 3.1 Vegetation and Soils The project lies in an area of primarily consisting of desert and desert shrub-land, with much of the nearby area covered by the Palmdale Regional Airport. No significant off-site impac ts are expected from the proposed action. Therefore, the potential for adverse im pacts to either soils or vegetation is minimal.
Criteria for evaluating impacts on soils and vegetation are provided in EPA's A Screening Procedure for the Impacts of Air Pollution Sources on Plants, Soils and Animals (EPA 1980). Table 3-1 lists the EPA suggested criteria for the gaseous pollutants emitted dire ctly from the proposed facility. These criteria are established for sensitive vegetation and crops exposed to the effects of the gaseous pollutants through direct exposure. Adverse impacts on soil systems resu lt more readily from the secondary effects of these pollutants' impacts on the stability of the soil sy stem. These impacts could include increased soil temperature and moisture stress and/or increased runo ff and erosion resulting fr om damage to vegetative cover. The modeled air concentrations for the proposed facility will be compared to these criteria to evaluate impacts on both soils and vegetation.
Table 3-1 EPA Criteria for Gaseous Pollutant Impacts on Natural Vegetation and Crops

Pollutant Averaging Time Minimum Impact Level for Affects on Sensitive Plants (μg/m 3 ) 4 hours 3,760 8 hours 3,760 1 month 564 NO 2

Annual 94 CO 1 week 1,800,000
1 hour 917 3 hours 786 SO 2 Annual 18PHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 3-2 July 2008 

### 3.2 Associated Growth PSD requires an assessment of the secondary impacts from applicable projects. There will be minimal associated growth expected during Project construction due to the relatively short-term (two year) duration and existence of a large construction labor force in th e region. Additionally, no long-term growth (i.e., general commercial, residential, industrial or other secondary growth in the area) is expected during operations due to the small labor forc e that will be required to operate this hybrid power plant. Therefore, no analysis of secondary impacts from asso ciated growth is needed for this Project.PHPP Appendix G.4, Class II Area Dispersion Modeling Protocol 4-1 July 2008 

## 4.0 References

Auer, A. H., 1978. Correlation of Land Use and Cover with Meteorological Anomalies. J. Appl. Meteor., Vol 17, pp 636-643.
Dennis, Richard, Handbook on Aerosols, 1976. En ergy Research and Development Administration Publication TID-26608, page 50.
EPA, 1980. A Screening Procedure for th e Impacts of Air Pollution Sources on Plants, Soils and Animals. OAQPS/EPA 450/2-81-078.
EPA, 1985. Guideline for Determination of Good E ngineering Practice Stack Height (Technical Support Document for the Stack Height Regulations), Revi sed. EPA Publication No. EPA-450/4/80-023R. Office of Air Quality Planning and Standards (OAQPS), Research Triangle Park, NC.
EPA, 1992 Procedures for Substituting Values for Mi ssing NWS Meteorological Data for Use in Regulatory Air Quality Models. D. Atkinson and R.F. Lee Research Triangle Park, NC 27711. July
EPA, 1995. Compilation of Air Pollution Emission Factor s. Volume I: Stationary Point and Area Sources. AP-42 Fifth Edition. OAQPS, Re search Triangle Park, NC 27711.
EPA, 1998. AERMET Users Guide ( http://www.epa.gov/scram001/metobsdata_procaccprogs.htm#aermet )
EPA, 2000 Meteorological Monitoring Guidanc e for Regulatory Modeling Applications (http://www.epa.gov/scram 001/guidance/met/mmgrma.pdf)
EPA, 2004. User's Guide for the AMS/EPA Regulat ory Model - AERMOD, EPA Publication Nos. EPA-454/B-03-001. OAQPS, Research Triangle Park, NC 27711.
EPA, 2005. Guideline on Air Quality Models (Revised). Codified in the Appendix W to 40 CFR Part 51. OAQPS, Research Triangle Pa rk, NC 27711. November.
EPA, 2008a. AERMOD Implementation Guide. http://www.epa.gov/scram001/7thconf/aermod/ aermod_implmtn_guide_09jan2008.pdf.
EPA, 2008b. AERSURFACE Users Guide (http://www.epa.gov/scram001/7thcon f/aermod/aersurface_userguide.pdf)
Hinds, William, C., 1982. Aerosol Technology, John Wiley & Sons, New York, NY, Page 381.
U.S. Federal Aviation Administration, 2005. Elec tronic Code of Federal Regulations - 14 CFR 77.28: Objects Affecting Navigable Airspace. http://ecfr.gpoaccess.gov/cgi/t/text/text-idx? &c=ecfr&tpl=/ecfrbrowse/Title14/14tab_02.tplPHPP Appendix G.4, Class II Area Dis persion Modeling Protocol July 2008 

## Attachment 1
AVAQMD Correspondence Related to the Cumulative Modeling InventoryPHPP Appendix G.4, Class II Area Dis persion Modeling Protocol July 2008PHPP Appendix G.4, Class II Area Dis persion Modeling Protocol July 2008