# Final Report



# SENSITIVITY ANALYSIS OF PVMRM AND OLM IN AERMOD

Alaska DEC Contract No. 18-8018-04

Submitted to: Alaska Department of En vironmental Conservation Division of Air Quality 410 Willoughby Avenue, Suite 303 Juneau, Alaska 99801-1795

September 2004

### FINAL REPORT



## SENSITIVITY ANALYSIS OF PVMRM AND OLM IN AERMOD

Alaska DEC Contract No. 18-8018-04

Prepared for
Alan E. Schuler, P.E. Alaska Department of Environmental Conservation Division of Air Quality 410 Willoughby Avenue, Suite 303 Juneau, Alaska 99801-1795

September 2004

Submitted by MACTEC Federal Programs, Inc.

5001 S. Miami Blvd., Suite 300 P.O. Box 12077 Research Triangle Park, NC 27709-2077

(919) 941-0333 FAX (919) 941-0234

### FINAL 09/30/2004 iii ACKNOWLEDGMENTS

This report of the sensitivity analysis of the PVMRM and OLM options in AERMOD was prepared by Roger W. Brode of MACTEC Fe deral Programs, Inc., Research Triangle Park, NC, under Alaska Department of Environmen tal Conservation (ADEC) Contract No. 18-8018- 04, with Alan Schuler as the ADEC project manager. The sensitivity analysis was also funded in part by BP Exploration (Alaska) , Inc (BPXA), with A lison Cooke as the BPXA project manager. MACTEC also appreciates the comments of Pat Hanrahan, formerly of Oregon DEQ, and Rob Wilson and Herman Wong of EPA Region 10.

### FINAL 09/30/2004 iv

### FINAL 09/30/2004

v TABLE OF CONTENTS
Page

ACKNOWLEDGMENTS ...........................................................................................................iii

TABLE OF CONTENTS ............................................................................................................. v
LIST OF FIGURES ..................................................................................................................... vi

LIST OF TABLES .....................................................................................................................viii

1.0 INTRODUCTION .................................................................................................................. 1

2.0 DESCRIPTION OF SENSITIVITY TESTS ....................................................................... 3 2.1 SOURCE DESCRIPTIONS............................................................................................ 3 2.2 MODELING OPTIONS ................................................................................................. 4 2.3 METEOROLOGICAL AND OZONE DATA ............................................................... 5 2.4 RECEPTOR DATA........................................................................................................ 6

3.0 SENSITIVITY ANALYSIS RESULTS ............................................................................... 9 3.1 SINGLE SOURCE SCENARIOS .................................................................................. 9 3.2 MULTIPLE-SOURCE SCENARIO............................................................................. 15 3.3 POINT VS. VOLUME AND AREA SOURCE COMPARISONS.............................. 17

4.0 SUMMARY AN D CONCLUSIONS .................................................................................. 55

5.0 REFERENCES ..................................................................................................................... 57

### FINAL 09/30/2004 vi LIST OF FIGURES Figure Page 2.1. Anchorage Area Terrain, Source and Recepto rs for Complex Terrain Scenarios............. 7 2.2. Receptor and Near-field Source Loca tions for Multiple Source Scenario ......................... 8 3.1. Ratios of Maximum Annual NO 2 

### Concentrations to Full Conversion ............................. 22 3.2. Ratios of Maximum 1-Hour NO 2 

### Concentrations to Full Conversion ............................. 22 3.3. Terrain Elevation vs. Downwind Distance for Maximum Annual NO 2 

### Averages for Diesel Generator (top) and Ga s Turbine (bottom) Sources .............................................. 23 3.4. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for 35m Buoyant Stack w ith 1g/s Emission Rate ................. 24 3.5. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for 35m Buoyant Stack with 50g/s Emission Rate ............... 25 3.6. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Generator Source with No Downwash ................ 26 3.7. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Generator Source with Downwash ...................... 27 3.8. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Ge nerator Source with Flat Terrain ..................... 28 3.9. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Ge nerator Source with Complex Terrain............. 29 3.10. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Ge nerator Source with Rural Dispersion ............. 30 3.11. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Ge nerator Source with Urban Dispersion............ 31 3.12. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Tu rbine Source with No Downwash........................ 32 3.13. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Turbine Source with Downwash.............................. 33 3.14. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Tu rbine Source with Flat Terrain............................. 34 3.15. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Tu rbine Source with Complex Terrain .................... 35 3.16. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Turb ine Source with Rural Dispersion .................... 36 3.17. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Turb ine Source with Urban Dispersion ................... 37 3.18. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for 35m Buoyant Stack w ith 1g/s Emission Rate ................. 38 3.19. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for 35m Buoyant Stack with 50g/s Emission Rate ............... 39 3.20. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Generator Source with No Downwash ................ 40

### FINAL 09/30/2004 vii 3.21. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Generator Source with Downwash ...................... 41 3.22. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Ge nerator Source with Flat Terrain ..................... 42 3.23. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Ge nerator Source with Complex Terrain............. 43 3.24. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Ge nerator Source with Rural Dispersion ............. 44 3.25. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Ge nerator Source with Urban Dispersion............ 45 3.26. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Tu rbine Source with No Downwash........................ 46 3.27. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Turbine Source with Downwash.............................. 47 3.28. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Tu rbine Source with Flat Terrain............................. 48 3.29. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Tu rbine Source with Complex Terrain .................... 49 3.30. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Turb ine Source with Rural Dispersion .................... 50 3.31. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Turb ine Source with Urban Dispersion ................... 51 3.32. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for 10m Non-buoyant Point Source...................................... 52 3.33. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for 10m Volume Source with Initial Sigmas=4.65m............ 53 3.34. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for 10m Area Source with Initial Sigma-z=4.65m ............... 54

### FINAL 09/30/2004 viii LIST OF TABLES

Table Page

2.1. Source Characteristics for AERMOD PVMRM Sensitivity Analysis................................ 4 2.2. Modeling Options Analyzed by Source Type..................................................................... 5 3.1. Comparison of Maximum Annual NO 2 

### Averages and Distance to Maximum for Full Conversion, ARM, OLM, and PVMRM for Single Source Scenarios............................. 12 3.2. Comparison of Maximum 1-Hour NO 2 

### Averages and Distance to Maximum for Full Conversion, ARM, OLM, and PVMRM for Single Source Scenarios............................. 13 3.3. Comparison of Maximum Annual and 1-Hour NO 2 

### Averages for Full Conversion, ARM, OLM, and PVMRM for Multiple-Source Scenario............................................... 16 3.4. Comparison of Maximum Annual NO 2 

### Averages and Distance to Maximum for Full Conversion, ARM, OLM, and PVMRM for 10 m Point, Volume and Area Sources ....... 18 3.5. Comparison of Maximum 1-Hour NO 2 

### Averages and Distance to Maximum for Full Conversion, ARM, OLM, and PVMRM for 10 m Point, Volume and Area Sources ....... 19

### FINAL 09/30/2004 1 1.0 INTRODUCTION

The purpose of this report is to document the results of a sensitivity analysis performed for the Plume Volume Molar Ratio Method (PVMRM) and Ozone Limiting Method (OLM) options in the AERMOD dispersion model. The PVMRM and OLM options for modeling the conversion of NO x 

### emissions to NO 2 

### have been incorporated into the AERMOD dispersion model. The PVMRM approach was originally developed as a post-processor for the ISCST3 model (Hanrahan, 1999a). A technical descri ption of the implemen tation of PVMRM in AERMOD is provided in the Addendum to th e AERMOD Model Formulation Document (Cimorelli, et al ., 2002), and user instructions on the application of the PVMRM and OLM options in AERMOD are provided in the A ddendum to the AERMOD User’s Guide (EPA, 2002).

The sensitivity analysis includes a comparison of NO 2 

### concentrations estimated by the PVMRM option to NO 2 

### concentrations based on the OLM option, Tier 1 screening assumption (full conversion of NO x 

### to NO 2 

### ), and Tier 2 screening (75 percent Ambient Ratio Method, ARM) across a range of meteorology and a range of source characteristics typical of NO x 

### sources. A description of the sensitivity test s is provided in Section 2. Results of the sensitivity analysis are presented in Section 3, and Section 4 provides a summar y and conclusions.

### FINAL 09/30/2004 2

### FINAL 09/30/2004 3 2.0 DESCRIPTION OF SENSITIVITY TESTS

This section includes a description of the sensitivity tests performed on the PVMRM and OLM options in the AERMOD dispersion model. The source parameters, modeling options, meteorological data and receptor data used in the sensitivity analysis are described in detail. The sensitivity analysis includes several tests i nvolving individual sources, and a multiple-source scenario.

2.1 SOURCE DESCRIPTIONS

A total of six different individual sources were modeled, incl uding a non-buoyant 10m point source, a standard 35m buoyant point source (used in EPA consequence analyses), a typical diesel generator source, a typical gas turbine s ource, a 10m volume source, and a 10m circular area source. The source parameters used for th ese single source scenarios are summarized in Table 2.1. A range of buoyancy and momentum fl uxes are represented by the point sources, with the diesel genera tor representing a rela tively low buoyancy/low momentum release, the 35m stack representing medium buoyancy and momentum, and the gas turbine representing relatively high buoyancy and momentum. The emi ssion rates for the diesel generator and gas turbine sources are considered typical for those source types. The 35m stack was modeled with two different emission rates to test the sensi tivity of the PVMRM and OLM algorithms to the NO x 

### emission rate.

In addition to the single source scenarios, a hypothetical multiple-source scenario based in part on an actual permit application was included in the sensitivity analysis to test the plume merging algorithm contained within PVMRM. Th e multiple-source scenario included a total of 65 point sources and 13 area sources, with 1,598 receptors.

### FINAL 09/30/2004 4 Table 2.1. Source Characteristics for AERMOD PVMRM Sensitivity Analysis

Point Sources:

Source Description Emission Rate (g/s) Stack Height (m) Exit Velocity

(m/s) Exit Temp.

(K) Stack Diameter (m) Buoyancy Flux a (m 4 /s 3 ) Momentum Flux a (m 4 /s 2 )10m Nonbuoyant Point 10 10 0.0 Ambient 0.0 0.0 0.0 35m Buoyant Stack 1 35 11.7 432 2.4 60.71 124.64 35m Buoyant Stack 50 35 11.7 432 2.4 60.71 124.64 Diesel Engine 5 26 50.0 727 0.3 6.88 21.14 Gas Turbine 30 31 63.0 750 2.4 565.25 2081.61 

### Volume Sources:

Source Description Emission Rate (g/s) Release Height (m) Initial Sigma-y

(m) Initial Sigma-z

(m) 10m Volume 10 10 0.1 to 9.3 0.1 to 9.3 

### Area Source:

Source Description Emission Rate (g/s) Release Height (m) Radius of Area (m) Initial Sigma-z

(m) 10m Circular Area 10 10 10 4.65

a 

### Buoyancy and momentum fluxes are base d on an ambient temperature of 273.16 K.

The 10m non-buoyant point source and 10m volum e source were included in the analysis to test the sensitivity on the algorithms to varyi ng the initial size of the volume source and to verify that the results for the volume source conv erged to the results for the point source as the initial dispersion parameters were decreased. A 10m circular area source was also included with an initial sigma-z of 4.65 for comparison with the 10m volume source of similar dimensions. The 20m width of the area source is comparable to a volume source with an initial sigma-y of 4.65m.

2.2 MODELING OPTIONS

The single sources were tested with va rious modeling options, including building downwash vs. no downwash, rural vs. urban disper sion, and flat vs. complex terrain. Not all sources were modeled for each modeling option. Table 2.2 summarizes the modeling options

### FINAL 09/30/2004 5 examined for each of the individual source types. A population of 250,000, which is the approximate population for Anchorage, Alaska, was used for the urban option. The complex terrain options were base d on terrain in the Anchorage, Alaska area. The flat vs. complex terrain sources were located about 10km southeast of Anc horage, with relatively flat terrain (including terrain below stack base) to the north and west of the source, and terrain risi ng fairly steeply within about 1.5 to 2km east of the source. The terrain for the Anchorage area is shown in Figure 2.1.

Table 2.2. Modeling Options Analyzed by Source Type
Source Description Modeling Options Meteorological Data 10m Non-buoyant Point Rural, Flat Terrain, No Downwash Anchorage 1999 10m Volume Source, Varying Initial Sigmas Rural, Flat Terrain Anchorage 1999

10m Circular Area Source Rural, Flat Terrain Anchorage 1999

35m Buoyant Stack, Varying Emission Rate Rural, Flat Terrain, No Downwash PadA 1991-95

Diesel Generator No Downwash vs . Downwash (Rural/Flat Terrain) Rural vs. Urban Dispersion (Flat Terrain/No Downwash) Flat Terrain vs. Complex Terrain (Rural/No Downwash) PadA 1991-95 PadA 1991-95 Anchorage 1999 Gas Turbine No Downwash vs. Downwash (Rural/Flat Terrain) Rural vs. Urban Dispersion (Flat Terrain/No Downwash) Flat Terrain vs. Complex Terrain (Rural/No Downwash) PadA 1991-95 PadA 1991-95 Anchorage 1999



### 2.3 METEOROLOGICAL AND OZONE DATA

Three different sets of mete orological data were used, de pending on the scenario. The basic single source scenarios were run using five years of site-spe cific meteorological data from the PadA installation on the North Slope of Alaska near Prudhoe Bay for the period 1991 through 1995. The five years of site-specifi c meteorological data included 10m wind speed,

### FINAL 09/30/2004 6 wind direction and temperature data, and we re processed through AERMET together with National Weather Service (NWS) surface and upper air data for Barrow, Alaska. The multisource scenario was run using one year of site-specific data from the same site in Prudhoe Bay for 1991, but differed from 1991 of the five-year dataset in that 10m sigma-theta and solar radiation data were also included. The third meteorological data set used for comparisons between flat and complex terrain consisted of one year (1999) of NW S surface and upper air meteorological data for Anchorag e, Alaska. The 1999 Anchorage me teorological data were also used for the comparisons between the 10m non-buoyant point source a nd the volume and area sources. The meteorological data used for th e single source scenarios are summarized in Table 2.2.

The site-specific meteorological data from PadA were processed using the most recent version of AERMET available from the SCRA M website, dated 03273. The following annual surface characteristics were used in processing th e PadA meteorological data, and were assumed to be constant across al l sectors: albedo = 0.30; Bowen ra tio = 1.5; surface roughness = 0.01m. The following annual surface characteristics were used in processing the Anchorage meteorological data, and were also assumed to be constant across all sectors: albedo = 0.25; Bowen ratio = 1.5; surface roughness = 0.10m.

The hourly ozone data used with the PadA meteorological data were collected at the same location as the meteorological data. The hour ly ozone data used with the 1999 Anchorage meteorological data were obtained from th e U.S. EPA CASTNET website for the Denali National Park site located about 250 km north of Anchorage. A value of 40 ppb was used to substitute for missing ozone data for both databases.

2.4 RECEPTOR DATA

The individual source scenarios were modele d with a polar grid of receptors centered on the source, with distances (in meters) of 50, 100, 150, 200, 300, 500, 750, 1000, 1500, 2000, 3000, 5000, 10000, 20000, and 30000, and 36 radials, for a total of 540 receptors. The use of a polar grid allowed for the results to be summari zed as a function of dist ance downwind from the

### FINAL 09/30/2004 7 source. The receptor elevations and hill height scales for the complex terrain scenarios were calculated using the most recent version of AERMAP (dated 03107) and 1-degree Digital Elevation Model (DEM) data for the Anchorage, Alaska area. Figure 2.1 shows the source and receptor locations and topography of the Anchorage area used for the comple x terrain scenarios, out to a distance of about 10,000 meters from the source. The receptor network used for the multiple-source scenario included discrete recept ors located at 25m intervals along the property boundary and gridded receptors at 100m intervals across a 4km-by-4km domain. A total of 1,598 receptors were included in the multiple-sour ce scenario. Figure 2.2 s hows the receptor and near-field source locations used in the multiple-source scenario. Additional background sources located beyond the 4km-by-4km receptor domain are not shown in Figure 2.2.

STACK

342000 344000 346000 348000 350000 352000 354000 356000 358000 360000 362000 3640006776000 6778000 6780000 6782000 6784000 6786000 6788000 6790000 6792000 6794000



### Figure 2.1. Anchorage Area Terra in, Source and Receptors for Complex Terrain Scenarios

### FINAL 09/30/2004 8 441500 442000 442500 443000 443500 444000 444500 445000 4455007801000 7801500 7802000 7802500 7803000 7803500 7804000



### Figure 2.2. Receptor and Near-field Source Lo cations for Multiple Source Scenario

### FINAL 09/30/2004 9 3.0 SENSITIVITY ANALYSIS RESULTS

The results of the PVMRM sens itivity analysis are presented in this section. The results for the single source scenarios are presented fi rst, and include comparisons of design values based on the highest annual and 1-hour average NO 2 

### concentrations, and comparisons of maximum concentrations as a function of distance downwind from the source.

3.1 SINGLE SOURCE SCENARIOS

Table 3.1 includes a comparison of maximum annual average NO 2 

### concentrations for each of the single source scenarios involving the 35m stack, diesel generator and gas turbine sources. Results are presented for full c onversion, ARM (0.75), OLM and PVMRM. The average OLM/FULL ratio for the single sour ce annual averages is 0.88, and the average PVMRM/FULL ratio for annual averages is 0.55. In many cases, the distance to maximum annual average is further downwind from the sour ce for PVMRM than for full conversion. This is due to the lower NO 2 

### /NO x 

### ratios close to the source for PVMRM.

Table 3.2 shows comparisons of maximum 1-hour average NO 2 

### concentrations for each of the single source scenarios presented in Table 3.1. The average OLM/FULL ratio for the single source 1-hour averages is 0.68, and the average PVMRM/FULL ratio for 1-hour averages is 0.56. The conversion ratios for OLM and PVMR M are also summarized in the form of bar charts in Figures 3.1 and 3.2 for annual av erages and 1-hour averages, respectively.

A comparison of the 35m stack with 1g/s emi ssion rate vs. 50g/s emission rate clearly shows the sensitivity of both OLM and PVMRM to the level of NO x 

### emissions. For the 1g/s source, the OLM option exhibited no ozone limiti ng effect, giving a ratio to full conversion of 1.0. The PVMRM option showed some effects of ozone limiting, but the ratio of 0.892 is very close to the equilibrium ratio of 0.90 for PVMR M. Both options show ed significantly more

### FINAL 09/30/2004 10 ozone limiting with the 50g/s source, as expect ed, with the OLM opti on providing about the same result as ARM, and the PVMRM opti on showing a more significant reduction.

Comparing the results for no downwash vs. downwash for the diesel generator and gas turbine sources, the maximum concentrations ar e much higher with downwash, as expected, and the conversion ratios are lower. The lower conve rsion ratios for OLM are most likely due to the higher ground-level NO x 

### concentrations with downwash. The lower conversion ratios for PVMRM are probably due to the fact that the maximum NO x 

### concentrations occur much closer to the source for the downwash cases, and th e plume volume corresponding to the maximum concentrations will therefore be smaller. The urban results (no downwash) tend to be slightly lower for the diesel generator annual averages than the rural results, except for the PVMRM option, whereas the urban results tend to be higher than rural results for the gas turbine. This is probably due to the difference in plume buoyancy be tween the two sources. The plume rise for the diesel generator is expected to be much lo wer than for the gas turb ine, and therefore the diesel generator is less likely than the gas turbine to experience lim ited mixing under stable conditions due to the urban mixing height.

The maximum annual average concentrations tend to be somewhat lower for the complex terrain scenario compared to flat terrain, with conversion rates being si milar between flat and complex terrain. The lower annual averages for complex terrain are due to the fact that the maximum ground-level NO 2 

### concentrations occur relatively cl ose to the source (300 meters for the FULL and OLM options), where the terrain is at or below stack base. The terrain elevations associated with the maximum ground-level conc entrations as a function of downwind receptor distance are shown in Figure 3.3. For all three options (FULL, OLM and PVMRM), the terrain is below stack base at the 300 and 500 meters recep tor distances for the diesel generator. The effect of terrain below stack base is to increa se the effective height of the plume above local ground, and thereby reduce the gr ound-level concentrations. The PVMRM option for the gas turbine source is the only exception to this pattern. In this case , the maximum annual average is slightly higher for complex terrain than for fl at terrain, and occurs as a downwind distance of 5,000 meters compared to 1,000 meters for the fl at terrain maximum. Figure 3.3 shows that

### FINAL 09/30/2004 11 receptors are below stack base at the 1,000 me ter distance for the FULL and OLM options, and well above stack base at the 5,000 me ter distance for the PVMRM option.

The effect of complex terrain is more clea rly evident in the maxi mum 1-hour averages (Table 3.2), with the complex terrain results bei ng much higher than the fl at terrain results. The PVMRM conversion ratios for 1-hour averages tend to be lower than for annual averages, which may be explained by the fact that the maxi mum 1-hour averages are controlled by stable conditions, during which the plume volume tends to be smaller. The OLM conversion ratios for 1-hour averages are also lower due to th e much higher ground-level concentrations.

The distance to maximum concentration for the PVMRM option tends to be at or beyond the distance to maximum for full conversion. This is consistent with th e fact that conversion ratios are lowest close to the source and in crease with downwind distance for PVMRM. The distance to maximum concentration for the OLM op tion is more likely to match the distance to maximum for full conversion, and is cl oser to the source in a few cases.

Figures 3.4 and 3.5 show the annual average NO 2 

### concentrations (top pane) and conversion ratios (bottom pane) as a function of distance downwind from the source for the 35m 1g/s and 50g/s sources, respectively. These fi gures clearly show the dependence of the OLM conversion ratio on the emi ssion rate and ground-level NO x 

### concentration, with no ozone limiting occurring for the 1g/s source, and with the dip in conversion ratio between 750-1000m roughly mirroring the increase in concentrations with distance for the 50g/s source. The dependence of the PVMRM convers ion ratio on emission rate is also shown, with much lower ratios (more ozone limiting) for the 50g/s sour ce. However, the dependence of the PVMRM conversion ratio on distance from the source is cl early shown in Figure 3.5 for the 50g/s source, with much smaller ratios close to the source wh ere the plume volume is relatively small, and increasing with distance to the equilibrium ratio of 0.90 beyond about 10 km.

### FINAL 09/30/2004 12 Table 3.1. Comparison of Maximum Annual NO 2 

### Averages and Distance to Maximum for Full Conversion, ARM, OLM, and PVMRM for Single Source Scenarios

Source Scenario Conversion Option Maximum NO 2 

### Concentration (μg/m 3 

### ) Distance to Maximum (m) Ratio to Full Conversion
FULL 0.112 750. 1.000 ARM 0.084 750. 0.750 OLM 0.112 750. 1.000 35m Stack, 1g/s Rural, No Downwash

PVMRM 0.100 750. 0.892 FULL 5.601 750. 1.000 ARM 4.201 750. 0.750 OLM 4.178 1000. 0.746 35m Stack, 50g/s Rural, No Downwash

PVMRM 1.537 3000. 0.274 FULL 2.927 500. 1.000 ARM 2.195 500. 0.750 OLM 2.807 500. 0.959 Diesel Generator Rural, No Downwash

PVMRM 1.236 1500. 0.422 FULL 54.375 50. 1.000 ARM 40.781 50. 0.750 OLM 21.498 50. 0.395 Diesel Generator Rural, Downwash

PVMRM 11.164 50. 0.205 FULL 2.338 500. 1.000 ARM 1.754 500. 0.750 OLM 2.226 500. 0.952 Diesel Generator Urban, No Downwash

PVMRM 1.317 2000. 0.563 FULL 3.682 300. 1.000 ARM 2.761 300. 0.750 OLM 3.604 300. 0.979 Diesel Generator Flat Terrain

PVMRM 1.606 1500. 0.436 FULL 3.228 300. 1.000 ARM 2.421 300. 0.750 OLM 3.179 300. 0.985 Diesel Generator Complex Terrain

PVMRM 1.511 1500. 0.468 FULL 0.441 1000. 1.000 ARM 0.331 1000. 0.750 OLM 0.440 1000. 0.997 Gas Turbine Rural, No Downwash

PVMRM 0.303 1500. 0.688 FULL 13.984 50. 1.000 ARM 10.488 50. 0.750 OLM 8.482 50. 0.607 Gas Turbine Rural, Downwash

PVMRM 2.849 750. 0.204 FULL 0.704 1500. 1.000 ARM 0.528 1500. 0.750 OLM 0.700 2000. 0.994 Gas Turbine Urban, No Downwash

PVMRM 0.591 3000. 0.839 FULL 0.636 750. 1.000 ARM 0.477 750. 0.750 OLM 0.636 750. 1.000 Gas Turbine Flat Terrain

PVMRM 0.465 1000. 0.732 FULL 0.571 750. 1.000 ARM 0.428 750. 0.750 OLM 0.571 750. 1.000 Gas Turbine Complex Terrain

PVMRM 0.479 5000. 0.838

### FINAL 09/30/2004 13 Table 3.2. Comparison of Maximum 1-Hour NO 2 

### Averages and Distance to Maximum for Full Conversion, ARM, OLM, and PVMRM for Single Source Scenarios

Source Scenario Conversion Option Maximum NO 2 

### Concentration (μg/m 3 

### ) Distance to Maximum (m) Ratio to Full Conversion
FULL 5.398 1000. 1.000 ARM 4.048 1000. 0.750 OLM 5.398 1000. 1.000 35m Stack, 1g/s Rural, No Downwash

PVMRM 4.858 1000. 0.900 FULL 269.899 1000. 1.000 ARM 202.424 1000. 0.750 OLM 151.088 3000. 0.560 35m Stack, 50g/s Rural, No Downwash

PVMRM 131.033 3000. 0.485 FULL 98.418 750. 1.000 ARM 73.813 750. 0.750 OLM 68.636 200. 0.697 Diesel Generator Rural, No Downwash

PVMRM 73.259 1000. 0.744 FULL 427.190 50. 1.000 ARM 320.393 50. 0.750 OLM 185.885 50. 0.435 Diesel Generator Rural, Downwash

PVMRM 147.120 50. 0.344 FULL 98.418 750. 1.000 ARM 73.813 750. 0.750 OLM 68.636 200. 0.697 Diesel Generator Urban, No Downwash

PVMRM 73.259 1000. 0.744 FULL 73.535 200. 1.000 ARM 55.151 200. 0.750 OLM 73.093 200. 0.994 Diesel Generator Flat Terrain

PVMRM 34.056 1000. 0.463 FULL 357.518 1500. 1.000 ARM 268.138 1500. 0.750 OLM 110.885 1500. 0.310 Diesel Generator Complex Terrain

PVMRM 94.448 5000. 0.264 FULL 51.910 3000. 1.000 ARM 38.933 3000. 0.750 OLM 35.904 2000. 0.692 Gas Turbine Rural, No Downwash

PVMRM 38.187 5000. 0.736 FULL 443.448 100. 1.000 ARM 332.586 100. 0.750 OLM 177.423 50. 0.400 Gas Turbine Rural, Downwash

PVMRM 138.667 750. 0.313 FULL 61.648 1500. 1.000 ARM 46.236 1500. 0.750 OLM 61.395 1500. 0.996 Gas Turbine Urban, No Downwash

PVMRM 55.025 1500. 0.893 FULL 38.605 750. 1.000 ARM 28.954 750. 0.750 OLM 38.605 750. 1.000 Gas Turbine Flat Terrain

PVMRM 18.481 750. 0.479 FULL 378.023 2000. 1.000 ARM 283.518 2000. 0.750 OLM 120.449 2000. 0.319 Gas Turbine Complex Terrain

PVMRM 150.036 2000. 0.397

### FINAL 09/30/2004 14 Figures 3.6 through 3.11 show the annual c oncentrations and c onversion ratios vs. distance for the diesel generato r scenarios, and Figures 3.12 through 3.17 show the results for the gas turbine scenarios. These figures show similar overall patterns for the dependence of conversion ratio on distance, with the OLM ratio being most dependent on the ground-level NO x 

### concentration, and the PVMRM ratio showing dependence on plume volume.

The effect of complex terrain is more noticea ble for the gas turbine source (Figure 3.15) than for the diesel generator source (Figure 3.9) . The gas turbine source shows a secondary maximum in the concentration plot for full conve rsion at a distance of 2,000 meters associated with plume impaction on the terrain to the east of the source (see Figure 3.3). All options show another maximum at a distance of 5,000 meters, al so associated with complex terrain impacts.

The deviation of the OLM value from th e full conversion valu e at the 2,000 meter receptor distance for the gas turbine (Figure 3.15) bears explanation. As shown in the conversion ratio plot in Figure 3.15, the conversion ratio for OLM drops to about 0.73 at that distance. The maximum NO 2 

### concentration for the OLM option occurs for terrain below stack base north-northwest (NNW) of the source, while the maximum NO 2 

### concentrations for full conversion and PVMRM occur for complex terr ain about 126 meters above stack base eastsoutheast (ESE) of the source (see Figure 3.3). Th e average concentration for the receptor to the NNW is based on a larger number of values associ ated with one of the peaks in the annual wind rose. The average concentration for the recepto r to the ESE is based on a smaller number of values with higher concentrations due to the co mplex terrain impact. Since the OLM conversion ratio is strongly dependent on the ground-level NO x 

### concentration, the ho urly conversion ratios are lower for the complex terrain impacts to th e ESE than for the impacts to the NNW. The NO 2 

### concentrations for the OLM option are nearly equal for the NNW and ESE receptors, but the conversion ratio is 0.71 for the complex terrain receptor to the ESE and 1.0 for the receptor below stack base to the NNW.

There is also a noticeable dip in the conversion ratio for PVMRM at the 2,000 meter distance shown in Figure 3.15. This can be expl ained by the fact that the maximum impacts occurring on complex terrain for receptors at and beyond 2,000 meters are a ssociated with stable

### FINAL 09/30/2004 15 atmospheric conditions, whereas the maximum imp acts for receptors located at or below stack base out to about 1,500 meters are associated with convective atmospheric conditions. The plume volume will tend to be much smaller for stable plumes than for convective plumes, resulting in lower conversion ratios for the complex terrain impacts.

Figures 3.18 through 3.31 show the 1-hour aver age concentrations and conversion ratios for the 35m stack, diesel generato r and gas turbine single source sc enarios. These figures show some similar trends as the annual averages, but th e curves tend to be less smooth as the results are more sensitive to variations in the cont rolling meteorological conditions and hourly ozone data at each distance. The effects of comple x terrain are more noticeable than for annual averages for both the diesel engine and gas tu rbine sources, with sharp peaks occurring at the distance where the plume impacts the terrain to the east. The peak appears to be slightly further downwind for the gas turbine than for the diesel generator. This is consistent with the higher plume rise for the gas turbine, resulting in the plume impacting the terrain further away.

3.2 MULTIPLE-SOURCE SCENARIO

Table 3.3 provides the results of the multip le-source scenario, showing the maximum annual average NO 2 

### concentrations and conversi on ratios, and maximum 1-hour NO 2 

### averages and ratios for each of the conversion options. Table 3.3 includes results for OLM based on individual plumes, and results for OLM based on combining plumes for six groups of sources based on proximity of the sources and the like lihood that plumes from those sources would quickly merge. The PVMRM option shows the lowe st conversion ratio for the annual averages, 0.62, which is slightly lower than the convers ion ratio for the OLM-Group option of 0.65. The OLM-Group ratio is somewhat lower than the OLM -Individual ratio, as exp ected. The result for the OLM option for individual plumes is similar to the result based on ARM.

It should be noted that while the annual average NO 2 

### concentrations presented in Table 3.3 exceed the 100 μg/m 3 

### National Ambient Air Quality Standard (NAAQS) for NO 2 

### , these values do not reflect predicted impacts from an actual facility. While the multiple-source scenario was based in part on actual sources, several changes and assu mptions were made to

### FINAL 09/30/2004 16 simplify the sensitivity analysis. Therefore, th e results do not reflect the impacts that would likely occur based on a more rigorous assessment.

Table 3.3. Comparison of Maximum Annual and 1-Hour NO 2 

### Averages for Full Conversion, ARM, OLM, and PVMR M for Multiple-Source Scenario

Averaging Period Conversion Option Maximum NO 2 

### Concentration (μg/m 3 

### ) Ratio to Full Conversion Annual Full Conversion ARM OLM-Individual OLM-Group PVMRM 166.6 125.0 126.3 108.0 103.8 1.00 0.75 0.76 0.65 0.62 1-Hour Full Conversion ARM OLM-Individual OLM-Group PVMRM 5,290.3 3,967.7 2,079.9 1,822.2 3,196.9 1.00 0.75 0.39 0.34 0.60

The results in Table 3.3 for 1-hour averages from the multiple-source scenario show much lower conversion ratios for the OLM opti ons (0.39 for individual plumes and 0.34 with combined plumes) than for the PVMRM option (0.60). This is not unexpected given the fact that the ozone limiting potential under the OLM options is strongly related to the maximum groundlevel concentration of NO x 

### , whereas the PVMRM ratio is related to the volume of the plume. As an example, for an elevated source the maxi mum 1-hour average concen tration is typically associated with light wind, convective conditions. The OLM ratio will tend to be low for this case because of the high ground-le vel concentration, whereas the PVMRM ratio will tend to be high due to the relatively large volume of the plume under convective conditions. It is worth noting that the 1-hour conversion ratio for PVMRM is similar to the ratio for annual averages, whereas the OLM ratios are quite dissimilar between a nnual and 1-hour averages.

### FINAL 09/30/2004 17 3.3 POINT VS. VOLUME AND AREA SOURCE COMPARISONS

Additional comparisons were made betw een a 10m non-buoyant point source, a 10m volume source with varying initia l dispersion coefficients (sig mas), and a 10m circular area source with an initial vertical dispersion coefficient (sigma-z). These comparisons provide additional sensitivity results for relatively low-level sources. They also provide a test of whether the volume source results converge to the point sour ce result as the initial dispersion coefficients are decreased, and provide a comparison of a circ ular area source to a volume source of similar dimensions.

The results for the point vs. volume and area source comparisons are provided in Table 3.4 for annual NO 2 

### averages and in Table 3.5 for 1-hour NO 2 

### averages. The initial sigma values for the volume sources apply to both lateral (sigma-y) and vertical (sigma-z) dispersion coefficients. For both averaging periods the result s for the volume source w ith initial sigmas of 0.1m are nearly identical to the point source results. As the in itial sigmas are increased, up to 9.3m, the maximum concentrations for the volu me sources also increa se. This result is reasonable as the larger initial sigmas will bri ng the plume to the ground quicker. For the two largest values of initial sigma, the distance to maximum concentration also drops from 100m to 50m.

The OLM annual average conversion ratios for the volume sources get smaller as the ground-level concentration increase s, as expected. The PVMRM ratios are nearly the same for the point source and the first three volume sources (0.1, 1.0, and 2.3m initial sigmas). The PVMRM ratio drops slightly between the 2.3m and 4.65m initial sigmas, due to the closer distance to maximum concentration for the 4.65m case, resulting in a smaller plume volume. The largest change in PVMRM conversion ratio o ccurs between the initial sigmas of 4.65m and 9.3m. The ratio increases for the larger initial sigma due to the corresponding increase in the plume volume resulting in more ozone available for conversion. The plume volume for volume sources incorporates the initial volume of the s ource defined by the initial sigmas in addition to the plume volume resulting from relative dispersion.

### FINAL 09/30/2004 18 Table 3.4. Comparison of Maximum Annual NO 2 

### Averages and Distance to Maximum for Full Conversion, ARM, OLM, and PVMRM for 10m Point, Volume and Area Sources

Source Scenario Conversion Option Maximum NO 2 

### Concentration (μg/m 3 

### ) Distance to Maximum (m) Ratio to Full Conversion
FULL 376.871 100. 1.000 ARM 282.654 100. 0.750 OLM 66.148 100. 0.176 10m Point

PVMRM 47.685 100. 0.127 FULL 376.974 100. 1.000 ARM 282.731 100. 0.750 OLM 66.162 100. 0.176 10m Volume Initial sigma = 0.1m

PVMRM 47.698 100. 0.127 FULL 383.590 100. 1.000 ARM 287.693 100. 0.750 OLM 67.036 100. 0.175 10m Volume Initial sigma = 1.0m

PVMRM 48.504 100. 0.126 FULL 409.933 100. 1.000 ARM 307.450 100. 0.750 OLM 71.006 100. 0.173 10m Volume Initial sigma = 2.3m

PVMRM 51.694 100. 0.126 FULL 742.539 50. 1.000 ARM 556.904 50. 0.750 OLM 114.185 50. 0.154 10m Volume Initial sigma = 4.65m

PVMRM 91.998 50. 0.124 FULL 1,085.476 50. 1.000 ARM 814.107 50. 0.750 OLM 156.531 50. 0.144 10m Volume Initial sigma = 9.3m

PVMRM 182.709 50. 0.168 FULL 751.711 50. 1.000 ARM 563.782 50. 0.750 OLM 97.653 50. 0.130 10m Area Initial sigmaz = 4.65m 20m wide circular area PVMRM 104.517 50. 0.139

### FINAL 09/30/2004 19 Table 3.5. Comparison of Maximum 1-Hour NO 2 

### Averages and Distance to Maximum for Full Conversion, ARM, OLM, and PVMRM for 10m Point, Volume and Area Sources

Source Scenario Conversion Option Maximum NO 2 

### Concentration (μg/m 3 

### ) Distance to Maximum (m) Ratio to Full Conversion FULL 11,106.540 50. 1.000 ARM 8,329.905 50. 0.750 OLM 1,178.703 50. 0.106 10m Point

PVMRM 1,258.679 50. 0.113 FULL 11,119.789 50. 1.000 ARM 8,339.842 50. 0.750 OLM 1,180.025 50. 0.106 10m Volume Initial sigma = 0.1m

PVMRM 1,260.190 50. 0.113 FULL 11,138.263 50. 1.000 ARM 8,353.697 50. 0.750 OLM 1,182.047 50. 0.106 10m Volume Initial sigma = 1.0m

PVMRM 1,262.501 50. 0.113 FULL 11,408.523 50. 1.000 ARM 8,556.393 50. 0.750 OLM 1,219.742 50. 0.107 10m Volume Initial sigma = 2.3m

PVMRM 1,295.209 50. 0.114 FULL 11,804.340 50. 1.000 ARM 8,853.255 50. 0.750 OLM 1,247.224 50. 0.106 10m Volume Initial sigma = 4.65m

PVMRM 1,326.409 50. 0.112 FULL 11,804.340 50. 1.000 ARM 8,853.255 50. 0.750 OLM 1,247.224 50. 0.106 10m Volume Initial sigma = 9.3m

PVMRM 1,326.409 50. 0.112 FULL 12,106.910 50. 1.000 ARM 9,080.184 50. 0.750 OLM 1,286.426 50. 0.106 10m Area Initial sigmaz = 4.65m 20m wide circular area PVMRM 1,474.794 50. 0.122

### FINAL 09/30/2004 20 The results for the area source with an initia l sigma-z of 4.65m are similar to the results for the volume source with initial sigmas of 4.65m. The full conversion results for the area source are about 1 percent higher than for the comp arable volume source for the annual averages. This difference is reasonable since the area s ource simulates a uniform emission rate over the 20m wide circular area, whereas the volume source is treated as a virtual point source with a peak emission density at the center of the source. This creates a higher emission density for the area source for the downwind portion of the source cl osest to the receptors. The slightly higher ground-level NO x 

### concentrations may contribute to the slightly lower NO 2 

### concentrations for the OLM option for the area source, with a lower conversion ratio reflecti ng more ozone limiting conditions.

The PVMRM option gives higher average NO 2 

### concentrations for the area source than for the corresponding volume source for both annual and 1-hour averages, by about 10 percent. This is related to the differences in the defi nition of the plume volume for area sources vs. volume sources. Since the area source simulates a uniform emission density across the source, the lateral dimension of the plume is defined as the projected width of the area source (which equals 20m for the circular area) plus 2 times the relative dispersion coefficient to account for lateral plume spread beyond the e dges of the source. The latera l dimension of the volume source plume is based on combining the initial sigma-y w ith the relative dispersion coefficient. This difference will result in slightly larger plume vol umes for area sources than for volume sources with similar dimensions, which will result in higher NO 2 

### /NO x 

### conversion ratios for PVMRM.

Figures 3.32, 3.33, and 3.34 compare the annual NO 2 

### concentration and conversion ratio plots vs. distance for the 10m point source, the 10m volume source with initial sigmas of 4.65m, and the 10m circular area source, respectively. Since these are low-level sources with peak impacts close to the source, the conversion ra tios for OLM and PVMRM show a more similar pattern than for the other sources with elevated plumes, with low conversion ratios close to the source and ratios increasing relatively smoothl y with increasing distance. However, the PVMRM conversion ratio increases more gradually with distance than OLM out to a distance of about 500m, with a steeper increas e in the ratio beyond that distance. As noted in previous discussions, the change in conversion ratio with distance for PVMRM is primarily controlled by

### FINAL 09/30/2004 21 the volume of the plume, whereas the conversion ratio for OLM is primarily controlled by the ground-level NO x 

### concentration.

### FINAL 09/30/2004 22 Figure 3.1. Ratios of Maximum Annual NO 2 Concentrations to Full Conversion

0 0.2 0.4 0.6 0.8

1 1.2

3 5 m

S tac

k

, 1

g/s

35

m

St

a c k,

5 0 g / s

Di

e sel Ge n e r at

o r No

D

W Diese l Genera t or

DW Diesel Generator URB

Di

e se

l Ge

n e r a to

r F l a t

D ies

e l Ge

ner

a tor CT

Ga

s T

ur b i n e No

DW Gas T u rbine DW

Ga

s Turb i n e URB

Ga

s T

u rb

i n e F lat Gas T u rbine CT

ScenarioRatio OLM PVMRM

Figure 3.2. Ratios of Maximum 1-Hour NO 2 Concentrations to Full Conversion

0 0.2 0.4 0.6 0.8

1 1.2

35m S t a c k,

1 g / s 35m Stack, 50g/s Diesel Generator No DW

D i e s e l Gen e ra t o r DW

Di

e sel Ge n erator U RB

Di

e s e l Ge

n e ra t o r Fl

a t

D i ese

l Genera t o r CT

Ga

s T

u rb

i n e No

DW

Ga

s T

u rb

i n e DW Gas T u rbine U RB Gas Turbin e Flat

Gas Turb i n e C

T

ScenarioRatio OLM PVMRM

### FINAL 09/30/2004 23 Terrain Elevation vs. Distance for Diesel Generator Annual Averages

0 50 100 150 200

1 10 100 1000 10000 100000 Distance (meters)Terrain Elevation (meters)

FULL OLM PVMRM Stack Base Elevation = 115m

Terrain Elevation vs. Distance for Gas Turbine Annual Averages

0 50 100 150 200 250 300

1 10 100 1000 10000 100000 Distance (meters)Terrain Elevation (meters)

FULL OLM PVMRM Stack Base Elevation = 115m



### Figure 3.3. Terrain Elevation vs. Do wnwind Distance for Maximum Annual NO 2 

### Averages for Diesel Generator (top) and Gas Turbine (bottom) Sources

### FINAL 09/30/2004 24 35m Stack, 1g/s - No Downwash - Annual

0.0001 0.001 0.01 0.1

1

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

35m Stack, 1g/s - No Downwash - Annual

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.4. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for 35m Buoyant Stack with 1g/s Emission Rate

### FINAL 09/30/2004 25 35m Stack, 50g/s - No Downwash - Annual

0.001 0.01 0.1

1 10

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

35m Stack, 50g/s - No Downwash - Annual

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.5. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for 35m Buoyant Stack with 50g/s Emission Rate

### FINAL 09/30/2004 26 Diesel Generator - No Downwash - Annual

0.001 0.01 0.1

1 10

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Diesel Generator - No Downwash - Annual

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.6. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Generator Source with No Downwash

### FINAL 09/30/2004 27 Diesel Generator - Downwash - Annual

0.01 0.1

1 10 100

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Diesel Generator - Downwash - Annual

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.7. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Generator Source with Downwash

### FINAL 09/30/2004 28 Diesel Generator - Flat Terrain - Annual

0.0001 0.001 0.01 0.1

1 10

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Diesel Generator - Flat Terrain - Annual

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.8. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Generator Source with Flat Terrain

### FINAL 09/30/2004 29 Diesel Generator - Complex Terrain - Annual

0.0001 0.001 0.01 0.1

1 10

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Diesel Generator - Complex Terrain - Annual

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.9. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Generator Source with Complex Terrain

### FINAL 09/30/2004 30 Diesel Generator - Rural - Annual

0.001 0.01 0.1

1 10

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Diesel Generator - Rural - Annual

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.10. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Generator Source with Rural Dispersion

### FINAL 09/30/2004 31 Diesel Generator - Urban - Annual

0.001 0.01 0.1

1 10

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Diesel Generator - Urban - Annual

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.11. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Generator Source with Urban Dispersion

### FINAL 09/30/2004 32 Gas Turbine - No Downwash - Annual

0.001 0.01 0.1

1

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Gas Turbine - No Downwash - Annual

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.12. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Turbine Source with No Downwash

### FINAL 09/30/2004 33 Gas Turbine - Do wnwash - Annual

0.01 0.1

1 10 100

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Gas Turbine - Do wnwash - Annual

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.13. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Turbine Source with Downwash

### FINAL 09/30/2004 34 Gas Turbine - Flat Terrain - Annual

0.001 0.01 0.1

1

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Gas Turbine - Flat Terrain - Annual

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.14. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Turbine Source with Flat Terrain

### FINAL 09/30/2004 35 Gas Turbine - Complex Terrain - Annual

0.001 0.01 0.1

1

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Gas Turbine - Complex Terrain - Annual

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.15. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Turbine Source with Complex Terrain

### FINAL 09/30/2004 36 Gas Turbine - Rural - Annual

0.001 0.01 0.1

1

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Gas Turbine - Rural - Annual

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.16. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Tu rbine Source with Rural Dispersion

### FINAL 09/30/2004 37 Gas Turbine - Urban - Annual

0.001 0.01 0.1

1

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Gas Turbine - Urban - Annual

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.17. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Turbine Source with Urban Dispersion

### FINAL 09/30/2004 38 35m Stack, 1g/s - No Downwash - 1hr

0.1

1 10

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

35m Stack, 1g/s - No Downwash - 1hr

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.18. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for 35m Buoyant Stack with 1g/s Emission Rate

### FINAL 09/30/2004 39 35m Stack, 50g/s - No Downwash - 1hr

1 10 100 1000

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

35m Stack, 50g/s - No Downwash - 1hr

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.19. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for 35m Buoyant Stack with 50g/s Emission Rate

### FINAL 09/30/2004 40 Diesel Generator - No Downwash - 1hr

1 10 100

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Diesel Generator - No Downwash - 1hr

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.20. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Generator Source with No Downwash

### FINAL 09/30/2004 41 Diesel Generator - Downwash - 1hr

1 10 100 1000

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Diesel Generator - Downwash - 1hr

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.21. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Generator Source with Downwash

### FINAL 09/30/2004 42 Diesel Generator - Flat Terrain - 1hr

1 10 100

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Diesel Generator - Flat Terrain - 1hr

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.22. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Generator Source with Flat Terrain

### FINAL 09/30/2004 43 Diesel Generator - Co mplex Terrain - 1hr

1 10 100 1000

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM



### Diesel Generator - Co mplex Terrain - 1hr

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.23. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Generator Source with Complex Terrain

### FINAL 09/30/2004 44 Diesel Generator - Rural - 1hr

1 10 100

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Diesel Generator - Rural - 1hr

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.24. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Generator Source with Rural Dispersion

### FINAL 09/30/2004 45 Diesel Generator - Urban - 1hr

1 10 100

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Diesel Generator - Urban - 1hr

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.25. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Diesel Generator Source with Urban Dispersion

### FINAL 09/30/2004 46 Gas Turbine - No Downwash - 1hr

0.1

1 10 100

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Gas Turbine - No Downwash - 1hr

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.26. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Turbine Source with No Downwash

### FINAL 09/30/2004 47 Gas Turbine - Do wnwash - 1hr

1 10 100 1000

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Gas Turbine - Do wnwash - 1hr

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.27. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Turbine Source with Downwash

### FINAL 09/30/2004 48 Gas Turbine - Flat Terrain - 1hr

0.1

1 10 100

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Gas Turbine - Flat Terrain - 1hr

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.28. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Turbine Source with Flat Terrain

### FINAL 09/30/2004 49 Gas Turbine - Complex Terrain - 1hr

0.1

1 10 100 1000

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Gas Turbine - Complex Terrain - 1hr

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.29. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Turbine Source with Complex Terrain

### FINAL 09/30/2004 50 Gas Turbine - Rural - 1hr

0.1

1 10 100

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Gas Turbine - Rural - 1hr

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.30. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Tu rbine Source with Rural Dispersion

### FINAL 09/30/2004 51 Gas Turbine - Urban - 1hr

0.1

1 10 100

1 10 100 1000 10000 100000 Distance (meters)Concentration (ug/m^3)

FULL OLM PVMRM

Gas Turbine - Urban - 1hr

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (meters)Ratio OLM/FULL PVM/FULL



### Figure 3.31. 1-Hour Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for Gas Turbine Source with Urban Dispersion

### FINAL 09/30/2004 52 10m Non-buoyant Point Source - No Downwash - Annual

0.1

1 10 100 1000

1 10 100 1000 10000 100000 Distance (m)Concentration (ug/m^3)

FULL OLM PVMRM

10m Non-buoyant Point Source - No Downwash - Annual

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (m)Ratio OLM/FULL PVM/FULL



### Figure 3.32. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for 10m Non-buoyant Point Source

### FINAL 09/30/2004 53 10m Volume Source - Initial Sigmas = 4.65m - Annual

0.1

1 10 100 1000

1 10 100 1000 10000 100000 Distance (m)Concentration (ug/m^3)

FULL OLM PVMRM

10m Volume Source - Initial Sigmas = 4.65m - Annual

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (m)Ratio OLM/FULL PVM/FULL



### Figure 3.33. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for 10m Volume Source with Initial Sigmas=4.65m

### FINAL 09/30/2004 54 10m Area Source - Initial Sigma-z = 4.65m - Annual

0.1

1 10 100 1000

1 10 100 1000 10000 100000 Distance (m)Concentration (ug/m^3)

FULL OLM PVMRM

10m Area Source - Initial Sigma-z = 4.65m - Annual

0 0.2 0.4 0.6 0.8

1 1.2

1 10 100 1000 10000 100000 Distance (m)Ratio OLM/FULL PVM/FULL



### Figure 3.34. Annual Average NO 2 

### Concentration (μg/m 3 

### ) vs. Downwind Distance (top) and Conversion Ratio (bottom) for 10m Area Source with Initial Sigma-z=4.65m

### FINAL 09/30/2004 55 4.0 SUMMARY AND CONCLUSIONS

This report presents results of a sensitivity analysis of the PVMRM and OLM options for NO x 

### to NO 2 

### conversion in the AERMOD dispersion mode l. Several single source scenarios were examined as well as a multiple-source scen ario. The average conversion ratios of NO 2 

### /NO x 

### for the PVMRM option tend to be lower than fo r the OLM option and for the Tier 2 option of 0.75 ARM. The sensitivity of the PVMRM and OLM options to emission rate, source parameters and modeling options appear to be reasonable and are as expected based on the formulations of the two methods. For a given NO x 

### emission rate and ambient ozone concentration, the NO 2 

### /NO x 

### conversion ratio for PVMRM is pr imarily controlled by the volume of the plume, whereas the conversion ratio for OLM is primarily contro lled by the ground-level NO x 

### concentration.

Overall the PVMRM option appears to provi de a more realistic treatment of the conversion of NO x 

### to NO 2 

### as a function of distance downwind from the source than OLM or the other NO 2 

### screening options (Hanrahan, 1999a; Hanr ahan, 1999b). No anomalous behavior of the PVMRM or OLM options was identified as a result of these sensitivity tests.

### FINAL 09/30/2004 56

### FINAL 09/30/2004 57 5.0 REFERENCES

Cimorelli, A. J., S. G. Perry, A. Venkatram, J. C. Weil, R. J. Paine, R. B. Wilson, R. F. Lee, W. D. Peters, R. W. Brode, and J. O. Paumie r, 2002: AERMOD: Description of Model Formulation (Version 02222). EPA 454/R-02- 002d. U. S. Environmental Protection Agency, Research Triangle Park, NC. Environmental Protection Agency, 2002: User’s Guide for the AMS/EPA Regulatory Model - AERMOD. EPA-454/R-02-001. U.S. Environm ental Protection Agency, Research Triangle Park, North Carolina 27711.
Hanrahan, P.L., 1999a. “The plume volum e molar ratio method for determining NO 2 

### /NO x 

### ratios in modeling. Part I: Methodology,” J. Air & Waste Manage. Assoc. , 49 , 1324-1331. Hanrahan, P.L., 1999b. “The plume volume molar ratio method for determining NO 2 

### /NO x 

### ratios in modeling. Part II: Evaluation Studies,” J. Air & Waste Manage. Assoc. , 49 , 1332- 1338.