Development and Evaluation of an Air 

Quality Modeling Approach for Lead 

Emissions from Piston-Engine Aircraft 

Operating on Leaded Aviation Gasoline 
EPA-420-R-10-007

February 2010

Assessment and Standards Division

Office of Transportation and Air Quality

U.S. Environmental Protection Agency

Prepared for EPA by

ICF International

and

T&B Systems

EPA Contract No. EP-C-06-094

Work Assignment No. 3-6

Development and Evaluation of an Air 

Quality Modeling Approach for Lead 

Emissions from Piston-Engine Aircraft 

Operating on Leaded Aviation Gasoline

NOTICE

This technical report does not necessarily represent final EPA decisions or 

positions. It is intended to present technical analysis of issues using data 

that are currently available. The purpose in the release of such reports is to 

facilitate the exchange of technical information and to inform the public of 

technical developments.
ACKNOWLEDGEMENTS 

This study would not have been possible without the dedicated efforts from a number of 

members of the project team. ICF team members included: Mark Lee, project manager who 

guided the overall efforts of the study and provided the framework and creative flexibility for the 

completion of the study; Edward Carr, principal investigator, lead the study’s air monitoring and 

modeling efforts providing valuable research and understanding of ambient air lead 

concentrations in the near-airport environment; Christopher Holder and Kristen Marin conducted 

extensive work preparing and assembling the comprehensive emission inventory and conducting 

the air quality modeling simulations; Scott Broten and Gary Clendenin provided their guidance 

and expertise for the soil and dust sampling and Mario Barrera conducted the soil sampling. 

Other important contributors to the study included T&B Systems’ Don Lehrman, Robert Baxter, 

Patrick Bush and Dave Yoho who provided detailed and careful air monitoring and Chester 

LabNet for their careful handling and analysis of filter samples. Keith Mew of California State 

University of Los Angeles and his team of graduate students collected valuable time-in-mode 

piston-engine aircraft activity data. Also, many homeowners in the neighborhood surrounding 

the Santa Monica Airport graciously volunteered their time and homes to allow ICF to collect 

air, soil, and dust samples. Martin Rubin assisted EPA in identifying homeowners willing to 

participate in the study. 

Other groups providing assistance to the study included the Santa Monica Airport personnel 

(Bob Trimborn, Rod Merl, and Stelios Makrides) who provided logistical support and access for 

the air monitoring study in addition to information regarding Santa Monica Airport’s pistonengine aircraft activity data. The South Coast Air Quality Management District’s (SCAQMD’s) 

Phil Fine provided air monitoring equipment for a portion of the study and shared air monitoring 

results from earlier air studies. Sumner Wilson, also of SCAQMD, helped with the air 

monitoring logistics and monitor set-ups. Tom Chico of SCAQMD provided the district’s lead 

emission inventory data used in part of the study. Bill Piazza of the Los Angeles Unified School 

District provided modeling inputs developed in an earlier study of the Santa Monica Airport. 

Finally, EPA’s Office of Transportation and Air Quality provided extensive review and comment 

throughout the study with respect to the air and soil monitoring and air quality modeling. 

Specific appreciation is given to Marion Hoyer, Rich Cook, and Meredith Pedde for providing 

extensive review, support, and thoughtful insight throughout the study. EPA’s Office of Air 

Quality Planning and Standards (Roger Brode and James Thurman) processed the on-site 2­

minute wind data for use in the air modeling and provided expert review and comment on the 

modeling methodology. Finally, EPA’s Region 9 (Matt Lakin, Arnold Den, Andre Villasenor, 

and Mike Bandrowski) provided extensive assistance with the public meetings, providing 

information and feedback from the public regarding the study. 

 iii 
Table of Contents
 

ACKNOWLEDGEMENTS.........................................................................................................................iii
 

TABLE OF CONTENTS.............................................................................................................................iv
 

LIST OF TABLES.......................................................................................................................................vi
 

LIST OF FIGURES ....................................................................................................................................vii
 

ACRONYMS AND ABBREVIATIONS ....................................................................................................ix
 

1 INTRODUCTION .....................................................................................................................................1
 

1.1 PROJECT BACKGROUND ............................................................................................................1
 

1.2 SELECTED LOCATION ................................................................................................................1
 

1.3 OVERVIEW OF APPROACH .........................................................................................................2
 

2 AIR MONITORING..................................................................................................................................3
 

2.1 OBJECTIVES ...............................................................................................................................3
 

2.2 OVERVIEW OF THE SANTA MONICA AIRPORT...........................................................................3
 

2.3 WINTER MONITORING PROGRAM..............................................................................................3
 

2.3.1 Approach...........................................................................................................................................3
 

2.3.2 Winter Program Monitoring Results.................................................................................................8
 

2.4 SUMMER MONITORING PROGRAM...........................................................................................15
 

2.4.1 Approach.........................................................................................................................................15
 

2.4.2 Summer Program Monitoring Results.............................................................................................17
 

3 SOIL AND DUST SAMPLING ..............................................................................................................19
 

3.1 SOIL SAMPLING .......................................................................................................................19
 

3.1.1 Approach.........................................................................................................................................19
 

3.1.2 Results.............................................................................................................................................22
 

3.2 DUST SAMPLING ......................................................................................................................24
 

3.2.1 Approach.........................................................................................................................................24
 

3.2.2 Results.............................................................................................................................................26
 

4 AIR QUALITY MODELING..................................................................................................................29
 

4.1 EMISSION INVENTORY.............................................................................................................29
 

4.1.1 Aircraft Sources ..............................................................................................................................29
 

4.1.2 On-road Sources..............................................................................................................................39
 

4.1.3 Area Source Emissions ...................................................................................................................42
 

4.1.4 Point Source Emissions...................................................................................................................45
 

4.1.5 Emissions Summary........................................................................................................................48
 

4.2 MODEL SELECTION AND CONFIGURATION..............................................................................48
 

4.2.1 Runway Configuration and Aircraft Wake Turbulence ..................................................................49
 

4.2.2 Terrain and Land Use......................................................................................................................52
 

4.2.3 Meteorological Data........................................................................................................................53
 

4.2.4 Background Ambient Conditions....................................................................................................54
 

4.2.5 Receptors.........................................................................................................................................54
 

4.2.6 Selected Modeling Scenarios ..........................................................................................................57
 

4.3 MODELING RESULTS ...............................................................................................................58
 

4.3.1 Winter Model-to-monitor Comparison ...........................................................................................58
 

4.3.2 Summer Model-to-monitor Comparison.........................................................................................59
 

4.3.3 Summary of the Model-to-monitor Comparison.............................................................................60
 

4.3.4 Full Year Modeling Results ............................................................................................................60
 

4.3.5 Maximum 3-month Average Modeled Concentrations...................................................................61
 

4.3.6 Sensitivity Analysis.........................................................................................................................66
 

4.3.7 AERMOD (07026) versus AERMOD (09292)...............................................................................68
 

 iv 
 

5 SUMMARY AND CONCLUSIONS ......................................................................................................71
 

5.1 CONCLUSIONS..........................................................................................................................71
 

5.2 IMPLICATIONS FOR OTHER AIRPORTS .....................................................................................72
 

6 REFERENCES ........................................................................................................................................75
 

Appendix A: Filter Analysis Reports Winter and Summer 2009 

Appendix B: Point Source Lead Emission Inventory Within 25 Km of Santa Monica Airport 

Appendix C: Winter 2009 Model-to-Monitor Results 

Appendix D: Summer 2009 Model-to-Monitor Results 

Appendix E: Year-long Modeling Results 

Appendix F: Sensitivity Analysis Figures 

 v 
List of Tables 

Table 2-1. Pb Air Concentrations from Winter Monitoring Program at SMO ........................... 8 

Table 2-2. Pb Air Concentrations from Summer Monitoring Program at Santa Monica 

Airport...................................................................................................................... 17 

Table 3-1. Soil Sampling........................................................................................................... 22 

Table 3-2. Soil Sample Locations, Descriptions, and Types in the Vicinity of Santa 

Monica Airport......................................................................................................... 23 

Table 3-3. Soil Sampling Metal Fractions Collected in the Vicinity of Santa Monica 

Airport (mg/kg)........................................................................................................ 24 

Table 3-4. Dust Sample Locations, Descriptions, and Types in the Vicinity of Santa 

Monica Airport......................................................................................................... 25 

Table 3-5. Dust Sampling Program........................................................................................... 26 

Table 3-6. Dust Sampling Measurements in Mass per Sample Area in the Vicinity of 

Santa Monica Airport............................................................................................... 26 

Table 4-1. Daily Aircraft Operations at Santa Monica Airport................................................. 30 

Table 4-2. Average Daily Aircraft Counts at Santa Monica Airport for 2008.......................... 30 

Table 4-3. Average Time-in-mode for Fixed-wing Piston-engine Aircraft at Santa 

Monica Airport......................................................................................................... 32 

Table 4-4. Fuel Consumption Rate (g/s) within Each Operational Mode at SMO ................... 33 

Table 4-5. Average Fuel Consumption for Helicopter Engine Type per LTO ......................... 33 

Table 4-6. Helicopter Time-in-mode Estimates........................................................................ 33 

Table 4-7. Pb Emissions (kg/yr) by Aircraft Type (2008) at SMO........................................... 35 

Table 4-8. Pb Emissions (kg/yr) by Aircraft Mode (2008) at SMO.......................................... 35 

Table 4-9. Details on the Emission Source Positions for Each Mode of Each Aircraft Type .. 35 

Table 4-10. Traffic Counts for the Three Major Roadways near Santa Monica Airport............ 41 

Table 4-11. Daily Bus Trips on Major Roadways near Santa Monica Airport........................... 41 

Table 4-12. Pb Emission Factors For Selected Area Sources ..................................................... 43 

Table 4-13. Total Area Source Pb Emissions, Across All Nine Area Source Grids................... 44 

Table 4-14. Facilities that Comprise 99.5% of Point Source Pb Emissions Within 

25 km of SMO ......................................................................................................... 46 

Table 4-15. Summary of the Lead Emissions Inventory for All Sources in the Vicinity of 

Santa Monica Airport (2008)................................................................................... 48 

Table 4-16. Surface Land Use Types (%) within 1 Kilometer Radius of SMO.......................... 52 

Table 4-17. Model-to-Monitor Comparison for Winter 2009 at Santa Monica Airport 

Using ASOS SMO (1-min wind data) ..................................................................... 58 

Table 4-18. Model-to-Monitor Comparison for Summer 2009 at Santa Monica Airport 

Using ASOS from SMO (1-min wind data) ............................................................ 59 

Table 4-19. Average Increase in Ambient Pb Concentration along 23rd St. from On-road 

Mobile Source Exhaust Emissions........................................................................... 62 

Table 4-20. Number of Hours over 3-month Period with Unstable, Neutral, and 

Stable Conditions at SMO ....................................................................................... 65 

Table 4-21. Ranges in Key Parameters for Pb Sensitivity Tests at Santa Monica Airport......... 68 

 vi 
List of Figures 

Figure 2-1. Santa Monica Airport and vicinity............................................................................. 4 

Figure 2-2. View from Santa Monica Airport towards the northeast and the observation viewing 

Figure 2-3. MiniVol (three) and HiVol instrumentation as deployed at the East Tarmac during a 

Figure 2-4. Sampling locations: East Tarmac (E) and the Clarkson monitor (C). The West 

Figure 2-6. Collocated instruments at the East Tarmac (bars are twice the standard deviation).
 

Figure 2-8. Daily average lead concentrations at the three monitoring sites during the winter 

Figure 2-10. Sampling locations during the Summer Monitoring Program: East Tarmac, Resident 

Figure 3-1. North runway area, nearby neighborhood, and near roadway soil and dust sample 

Figure 4-3. The Horizontal and vertical positions of emissions from fixed wing aircraft and 

Figure 4-4. The Horizontal and vertical positions of emissions from fixed wing aircraft and 

Figure 4-5. Major roadways in close proximity to Santa Monica Airport explicitly modeled in 

Figure 4-6. Hourly distribution of traffic on three major roadways surrounding Santa Monica 

Figure 4-9. Ambient lead monitoring in the South Coast Air Basin (April 2004 – March 2006).
 

Figure 4-12. 3-month daily average general aviation (GA) and air taxi (AT) activity at Santa 

Figure 4-14. 3-month rolling average concentrations for the 12 highest receptor locations for 

deck............................................................................................................................ 5 

portion of the winter monitoring program. ................................................................ 5 

Tarmac site is located at the other end of the runway (not shown). .......................... 7 

Figure 2-5 a and b. Collocated HiVol versus MiniVol winter monitoring................................ 10 

.................................................................................................................................. 11 

Figure 2-7. Full-day (24-hour) monitoring versus 18-hour monitoring. .................................... 13 

monitoring program. ................................................................................................ 14 

Figure 2-9. Mean and mean difference (error bars) for collocated MiniVols. ........................... 14 

1, Resident 2, and Maintenance Shed (M)............................................................... 16 

Figure 2-11. Location of the HiVol sampler at the Residence 1. ................................................. 17 

Figure 2-12. Location of the HiVol sampler at the Residence 2. ................................................. 17 

locations. .................................................................................................................. 20 

Figure 3-2. South runway, observation deck, and Clover Park soil sampling sites. .................. 21 

Figure 4-1. Hourly activity for piston-engine aircraft at Santa Monica Airport. ....................... 32 

Figure 4-2. Location of each emissions source for each mode by type of aircraft..................... 36 

helicopters (view is towards the east). ..................................................................... 37 

helicopters (view is towards the west)..................................................................... 38 

AERMOD. ............................................................................................................... 40 

Airport...................................................................................................................... 42 

Figure 4-7. Point source facilities emitting Pb near Santa Monica Airport................................ 46 

Figure 4-8. Land use in the Vicinity of the Santa Monica Airport............................................. 53 

.................................................................................................................................. 55 

Figure 4-10. On-airport air quality modeling receptors................................................................ 55 

Figure 4-11. Air quality modeling receptors in the vicinity of SMO. .......................................... 56 

Monica Airport......................................................................................................... 58 

Figure 4-13. Upwind/downwind receptors along 23rd St. near Santa Monica Airport................ 62 

2008 at Santa Monica Airport.................................................................................. 63 

Figure 4-15. 3-month rolling average wind speed at SMO. ......................................................... 64 

 vii 
Figure 4-16. 3-month rolling average convective mixing height at SMO.................................... 64 

Figure 4-17. 3-month rolling average mechanical mixing height at SMO................................... 65 

Figure 4-18. Frequency of wind direction at SMO....................................................................... 66 

Figure 4-19. Sensitivity tests for the maximum 3-month average period (June-August)............. 67 

Figure 4-20. Locations of top 12 receptors found in sensitivity tests........................................... 67 

Figure 4-21. Ranked absolute value of percent difference of AERMOD (09292) and AERMOD 

(07026) for single-engine run-up emissions on March 29, 2009............................. 69 

 viii 
 

Acronyms and Abbreviations 

AERMET AERMET is a meteorological data preprocessor for AERMOD 

AERMOD Atmospheric dispersion modeling system 

AERSURFACE A tool that processes land cover data to determine the surface characteristics 

AQMP Air Quality Management Plan 

ASOS Automated Surface Observation System 

avgas Leaded aviation gasoline 

CALINE3 A versatile dispersion model for predicting air pollutant levels near highways and 

arterial streets 

Caltrans California Department of Transportation 

CARB California Air Resources Board 

CEIDARS California Emission Inventory and Reporting System 

CRPAQS California Regional Particulate Air Quality Study 

DEM Digital Elevation Model 

DTIM Direct Travel Impact Model 

EDMS Emission Dispersion Modeling System 

EPA Environmental Protection Agency 

FAA Federal Aviation Administration 

FOE Friends of the Earth 

FRM Federal Reference Method 

g/gal Grams/gallon 

g/s Grams/second 

GIS Geographic information system 

HEI Health Effects Institute 

HiVols High-volume particulate samplers 

IMS95 1995 Integrated Monitoring Study 

kg kilogram 

LPG Liquefied petroleum gas 

LT Local time 

m Meters 

m/s Meters/second 

MATES-III Multiple Air Toxics Exposure Study III 

MDL Minimum detection limit 

mg Milligram 

MiniVols Low-volume particulate samplers 

NAAQS National Ambient Air Quality Standard 

NEI National Emissions Inventory 

ng/m3 Nanograms per cubic meter 

NLCD92 National Land Cover Data 1992 

OAQPS Office of Air Quality Planning and Standards 

Pb Lead 

PM10 Particulate matter, 10 micrometers and smaller 

PM2.5 Particulate matter, 2.5 micrometers and smaller 

s Seconds 

SCAG Southern California Association of Governments 

SCAQMD South Coast Air Quality Management District 

SCCs Source Classification Codes 

SIC Source industrial classification 

 ix 
SMO FAA designator for Santa Monica Airport 

TSP Total suspended particulate 

USGS U.S. Geological Survey 

XRF X-ray fluorescence 

L Monin-Obukov Length 

 x 
1 INTRODUCTION 

1.1 PROJECT BACKGROUND 

Tetraethyl lead is used as an additive in aviation fuel for most piston-engine powered aircraft. The 2005 

National Emissions Inventory (NEI) estimates that annual lead (Pb) emissions from the use of leaded 

aviation gasoline (commonly referred to as leaded “avgas”) are 653 tons, or approximately 50 percent of 

the air emission inventory for lead. Lead is also present as a trace contaminant in gasoline and diesel fuel 

and is a component of lubricating oil. Additional mobile sources of Pb include automobile brake wear, 

tire wear, and loss of Pb wheel weights. 

In October 2006, EPA received a petition from Friends of the Earth (FOE) requesting that the Agency 

find that aircraft Pb emissions may reasonably be anticipated to endanger the public health and/or welfare, 

and to take action to control Pb emissions from piston-engine aircraft. To evaluate this petition, EPA 

surveyed the available literature and found that there are few monitoring or modeling studies of Pb 

concentrations near airports servicing piston-engine aircraft that operate on leaded aviation gasoline. The 

purpose of this local-scale airport modeling and monitoring study is to investigate near source 

concentration gradients in ambient air attributable to lead from the combustion of leaded aviation gasoline 

and to investigate changes in these gradients with changes in emissions. The results of this study may be 

used to draw inferences at other locations, and to provide methods for evaluating air quality impacts from 

general aviation airports on local Pb concentrations. The results from this study provide information 

which could be used in a multimedia exposure and risk assessment of Pb near airports servicing avgasfueled aircraft. 

1.2 SELECTED LOCATION 

This study included both monitoring and modeling of Pb near an airport which services a large number of 

piston-engine aircraft operating on leaded avgas. Several airports which service a large number of avgas 

fueled aircraft were considered for this study. One of the airports considered was the Santa Monica City 

Airport (SMO), which was identified as an airport with relatively high lead emissions from general 

aviation activity. In 2002, 363 kg/yr (0.4 tons per year) of Pb was emitted at the Santa Monica Airport, as 

identified in EPA’s National Emissions Inventory. The Santa Monica Airport was selected for this study 

based on a number of factors that were anticipated to lead to the successful collection of Pb monitoring 

samples and reduce uncertainty in the air quality modeling. Among the most important factors were: 

	 The local air agency, South Coast Air Quality Management District (SCAQMD), had conducted 

recent air monitoring for Pb at and near the Santa Monica Airport; 

	 SCAQMD would be able to provide some air monitoring equipment; 

	 Santa Monica Airport was established in 1915 and thus soil samples would likely include 

contributions of Pb from long-term atmospheric deposition; 

	 There are no other nearby large sources of Pb emissions; 

	 Santa Monica Airport’s operators supported the study and ICF had conducted previous 

environmental studies at the airport with much cooperation from the airport staff; 

	 A large residential population (150,000 within two miles) surrounds the Airport; 

	 An earlier air quality modeling study was conducted at the Santa Monica Airport (Piazza, 1999); 

and 

	 The airport has a single runway configuration. 

 1 
1.3 OVERVIEW OF APPROACH 

The primary purpose of the study was to develop and evaluate an air quality modeling approach that 

could be used to evaluate local-scale concentrations of lead in the vicinity of an airport where pistonengine aircraft operate. Air monitoring was conducted to evaluate the performance of the air modeling 

approach. Soil and dust measurements for Pb and other metals were also made to help establish the 

fraction of lead in re-entrained road dust for roadways in the vicinity of the airport and to explore the 

potential for a gradient in the ambient air Pb concentration with distance from the airport. 

The study also included an assessment of the maximum 3-month average Pb concentration and model 

sensitivity tests. The maximum 3-month average Pb concentration was evaluated in order to compare the 

model output with the National Ambient Air Quality Standard for Lead which is 0.15 μg/m3

, reported as 

the maximum 3-month average concentration. 

Based on the results of this study, an outline of a generalized modeling approach has been developed that 

can be applied to general aviation facilities across the United States. 

This report summarizes the findings from the: 

 Air, soil and dust monitoring performed at Santa Monica Airport; 

 Development of the emission inventory and air quality modeling inputs; 

 Results of the model-to-monitor comparison; 

 Annual and maximum 3-month average modeling results and; 

 Model sensitivity analysis. 

The report is divided into four primary discussion areas: air monitoring methodology and results (Chapter 

2), soil and dust sampling methodology and results (Chapter 3), air quality modeling methodology and 

results (Chapter 4), and a conclusion on the findings and implications from the study results (Chapter 5). 

The references for the report are provided in Chapter 6. 

 2 
2 AIR MONITORING 

2.1 OBJECTIVES 

The objectives of the air monitoring program were: to provide Pb measurements for comparison with air 

quality modeling, to assist in the quantification of the contribution of Pb from general aviation emissions 

to local air quality, and to provide information about the gradient in Pb concentrations with distance from 

the airport. The air monitoring section is divided into three subsections: (1) an overview of the Santa 

Monica Airport location, (2) a description of the winter monitoring program and associated results, and 

(3) a description of the summer monitoring program and associated results. 

2.2 OVERVIEW OF THE SANTA MONICA AIRPORT 

Established in 1919, the Santa Monica Airport is the oldest community airport operating in Los Angeles 

County. The airport is one of the busiest single runway airports in the nation, and provides for numerous 

aviation-related businesses, including fixed-based operators, supply services, and aircraft maintenance. 

The airport occupies over 200 acres (0.81 square kilometers) in the southeastern portion of the City of 

Santa Monica, with the City’s southern boundary coinciding with the airport’s southern property line. A 

triangular portion (approximately 34 acres) of the site’s eastern boundary lies within the City of Los 

Angeles. This land is owned in fee by the City of Santa Monica. 

The site is served by arterial streets with primary access via South Bundy Dr. which borders the airport’s 

eastern boundary. Twenty-third St., which adjoins the airport’s western boundary, connects between 

Ocean Park and Venice Boulevards. Airport access to the north is accomplished by traversing south from 

Ocean Park Blvd. via Twenty-eighth or Thirty-first St. Airport Ave., which parallels the site’s southern 

boundary, provides internal access to the airport. 

The airport is surrounded to the south, east, and west by residential neighborhoods. Commercial 

structures and recreational facilities predominate to the north. The airport is situated on a plateau above 

the surrounding community; the local topography provides a relatively horizontal land formation which 

accommodates a long runway across the length of the property. Along the terminus of the runway, the 

land mass slopes sharply in a downward trend producing a change in elevation of more than thirty feet. 

Figure 2-1 presents an aerial view of the airport and surrounding community, with the airport property 

line indicated in magenta and the airport fence line along the southern border of the airport indicated in 

yellow. Figure 2-2 provides a view towards the northeast of the observation deck and of a plane taxiing 

for departure on runway 21. 

2.3 WINTER MONITORING PROGRAM 

2.3.1 Approach 

The winter monitoring program was conducted not only to measure Pb concentrations for the air quality 

modeling, but also to test whether a lower cost monitoring program could be deployed that could collect 

adequate samples for measuring Pb using MiniVols (low volume samplers). MiniVols operate with lower 

cost than HiVol (high volume) samplers and have the added flexibility of operating without commercial 

power (i.e., via battery). Figure 2-3 below shows the MiniVol (three total devices) and HiVol 

instrumentation used. 

 3 
Source: Aerial provided by City of Santa Monica. 

Figure 2-1. Santa Monica Airport and vicinity. 
Source: ICF International 

Figure 2-2. View from Santa Monica Airport towards the northeast and the observation 

viewing deck. 

Source: T&B Systems 

Figure 2-3. MiniVol (three) and HiVol instrumentation as deployed at the East Tarmac 

during a portion of the winter monitoring program. 

 5 
 

The winter monitoring period encompassed two 4-day periods—Friday though Monday over successive 

weekends—March, 12–15 and 27–30, 2009. The program focused on weekends because the Santa 

Monica Airport historically has higher general aviation activity on weekends than on weekdays. The 

weekend period encompassed three 24-hour sampling periods: Friday to Saturday, Saturday to Sunday, 

and Sunday to Monday. Filter samples were changed out at approximately the same time on each of the 

days, with the operating parameters documented in logs (Appendix A). 

Three monitoring sites comprised the network for the winter program. The locations of the two downwind 

sites relative to the runway and each other are shown in Figure 2-4. The prevailing wind flow is onshore 

during the day when most aircraft activity takes place. Under this scenario, the West Tarmac site is 

generally upwind, and the East Tarmac and Clarkson sites are downwind. T&B Systems conducted the 

deployment and operation of the monitoring system. 

The MiniVol samplers were operated in the total suspended particulate (TSP) mode at all three sites. In 

addition to the MiniVol sampler operated at each of the three sites, a fourth MiniVol sampler was 

operated to rotate between the three network sites, and a fifth MiniVol sampler was operated only during 

airport operational hours1

 at the East Tarmac. This allowed the gathering of more information on 

instrument precision and bias amongst the samplers. Samples were collected from the fifth MiniVol only 

during airport operational hours to provide data related specifically to the time period when piston-engine 

aircraft activity occurs at the airport for comparison to 24-hour average lead concentrations at this 

location. 

The MiniVol samplers are easily portable (battery operated) and can easily be sited at any location that 

has adequate exposure and is free from vandalism. There have been a number of field studies in which 

MiniVols have been collocated with Federal Reference Method (FRM) analyzers and compared 

favorably. These date back to the 1995 Integrated Monitoring Study (IMS95), which was a prelude to the 

1999 through 2001 California Regional Particulate Air Quality Study (CRPAQS) (Solomon, P. and 

Magliano K., 1999; Air Resource Specialists, 2000 and 2001) in which over 100 of the MiniVol samplers 

were used over the 14 month measurement period. These comparisons were all done using a PM10 

sampling head and were focused on particulate matter. Nominal flow rates for MiniVols are five liters per 

minute. 

The laboratory selected to analyze the air samples collected for this study was Chester LabNet 

(www.chesterlabnet.com). XRF (X-ray fluorescence) analysis was used because the method has a 

minimum detection limit (MDL) of less than 4 ng/m3

 at the nominal flow rate over 24 hours. By 

comparison, Fine (2007, 2008) reported TSP Pb concentrations at the East Tarmac in samples collected in 

March through July that ranged from 27 to 149 ng/m3

. Thus, samples collected with the MiniVol while it 

operated properly over a 24-hour cycle were anticipated to have sufficient mass to exceed the detection 

limit. 

In addition to the MiniVol, the availability of commercial power at the East Tarmac location made an 

intercomparison between the MiniVol and a TSP HiVol sampler possible, which is the Federal Reference 

Method (FRM) for Pb. This provided: (1) a reference to the FRM method for Pb sampling, and (2) a 

collocated site for the MiniVol TSP method with the FRM method. The HiVol TSP instrument was 

operated on the same schedule as the MiniVol sampler. 

1

 The Santa Monica Airport only permits departures during the hours of 0700-2300 Monday through Friday and 

0800-2300 Saturday and Sunday, except for emergencies. 

 6 
 

Source: GoogleEarth. 

Figure 2-4. Sampling locations: East Tarmac (E) and the Clarkson monitor (C). The West Tarmac 

site is located at the other end of the runway (not shown). 

Four filter blanks (two HiVol and two MiniVol) were analyzed during the winter program.2

 The purpose 

of the filter blanks is to evaluate filter media concentrations of Pb. Ideally, the concentration of lead in 

blank samples is sufficiently low so that their values are not a significant contributor to sample values. 

However, when ambient concentrations approach method detection limit values, blank values are 

important to characterize. Calibrations for all of the equipment were performed using certified flow 

standards. Pb samples were analyzed by Chester LabNet using XRF. The filter media was Teflon and 

quartz for the MiniVol and HiVol samples, respectively. The Teflon filter was used for the MiniVols to 

yield the lowest detection limit possible for the smaller sample mass, but analysis of these filters can 

present challenges due to their relatively low optical density which causes artifacts to appear when using 

the XRF measurement technique. Quartz filters were used in the HiVol to minimize particle bounce. 

2

 A third MiniVol filter was analyzed as a filter blank. 

 7 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2.3.2 Winter Program Monitoring Results 

Individual Monitoring Results 

Table 2-1 summarizes the ambient Pb air monitoring data collected during the winter monitoring program 

at the Santa Monica Airport. The table shows the location of the monitor, the starting date, the starting 

time, the duration of the sample, the Pb concentration, the day of the week in which the sample was 

collected, the type of monitor used to collect the data, and a description of any problems or invalid 

measurements in the “Comments” column. 

Table 2-1. Pb Air Concentrations from Winter Monitoring Program at SMO 

Sample 

ID Site 

Start 

Date 

Start 

Time 

Duration 

(hh:mm) 

Day of 

Week 

Pb 

(ng/m3

) Type Comments 

09-Q46 E.Tarmac 3/12/2009 12:00 07:45 Thursday 24.6 HiVol 

09-T1041 E.Tarmac 3/12/2009 12:06 07:30 Thursday 15.6 MiniVol 

09-T1042 E.Tarmac 3/12/2009 12:08 07:19 Thursday 16.6 MiniVol 

09-T1043 E.Tarmac 3/12/2009 12:05 Unknown Thursday MiniVol Accidentally turned off, 

not used in analysis 

09-T1045 E.Tarmac 3/12/2009 12:00 07:30 Thursday 13.8 MiniVol 

09-T1060 E.Tarmac 3/12/2009 12:00 07:19 Thursday 11.0 MiniVol 

09-Q47 E.Tarmac 3/13/2009 8:04 24:41 Friday 45.6 HiVol 

09-T1048 W.Tarmac 3/13/2009 8:23 24:53 Friday 11 MiniVol 

09-T1052 E.Tarmac 3/13/2009 7:22 24:56 Friday 34 MiniVol 

09-T1055 Residential 3/13/2009 8:46 24:59 Friday 40 MiniVol 

09-T1058 E.Tarmac 3/13/2009 7:19 15: 41 Friday 48 MiniVol 11 p.m. shutoff 

09-T1059 E.Tarmac 3/13/2009 7:29 25:08 Friday 25 MiniVol 

09-Q48 E.Tarmac 3/14/2009 9:00 23:38 Saturday 53 HiVol 

09-T1044 E.Tarmac 3/14/2009 8:24 23:53 Saturday 36 MiniVol 

09-T1046 Residential 3/14/2009 9:43 23:53 Saturday 29 MiniVol 

09-T1050 W.Tarmac 3/14/2009 9:23 23:40 Saturday 2 MiniVol Accidentally turned off, 

not used use in the 

analysis 

09-T1051 E.Tarmac 3/14/2009 8:35 14:25 Saturday 53 MiniVol 11 p.m. shutoff 

09-T1040 E.Tarmac 3/15/2009 9:25 23:52 Sunday 46 MiniVol Not used in the 

analysis – location of 

sample measurement 

uncertain 

09-Q49 E.Tarmac 3/15/2009 8:48 23:54 Sunday 77 HiVol 

09-T1047 W.Tarmac 3/15/2009 9:09 24:03 Sunday 6 MiniVol 

09-T1049 E.Tarmac 3/15/2009 8:33 14:27 Sunday 99 MiniVol 11 p.m. shutoff 

09-T1054 Residential 3/15/2009 9:43 23:47 Sunday 50 MiniVol 

09-T1057 Residential 3/15/2009 9:32 23:54 Sunday 38 MiniVol 

09-T1061 W.Tarmac 3/15/2009 8:23 24:07 Sunday <detection 

limit 

MiniVol below minimum 

detection limit – which 

is 3.2 ng/m3

 at 68% 

confidence level 

09-Q51 E.Tarmac 3/27/2009 8:00 25:02 Friday 83 HiVol 

09-T1062 E.Tarmac 3/27/2009 7:32 25:07 Friday 49 MiniVol 

09-T1063 E.Tarmac 3/27/2009 7:40 15:20 Friday 88 MiniVol 11 p.m. shutoff 

 8 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 2-1. Pb Air Concentrations from Winter Monitoring Program at SMO 

Sample 

ID Site 

Start 

Date 

Start 

Time 

Duration 

(hh:mm) 

Day of 

Week 

Pb 

(ng/m3

) Type Comments 

09-T1064 E.Tarmac 3/27/2009 7:45 25:10 Friday 73 MiniVol 

09-T1065 W.Tarmac 3/27/2009 8:22 25:08 Friday 8 MiniVol 

09-T1066 Residential 3/27/2009 8:38 25:14 Friday 46 MiniVol 

09-Q52 E.Tarmac 3/28/2009 9:12 23:39 Saturday 39 HiVol 

09-T1067 E.Tarmac 3/28/2009 8:45 23:49 Saturday 30 MiniVol 

09-T1068 E.Tarmac 3/28/2009 8:52 14:08 Saturday 46 MiniVol 11 p.m. shutoff 

09-T1069 W.Tarmac 3/28/2009 9:28 23:53 Saturday <detection 

limit 

MiniVol below minimum 

detection limit, which is 

3.2 ng/ m3

 at 68% 

confidence level 

09-T1070 W.Tarmac 3/28/2009 9:35 23:37 Saturday 5 MiniVol 

09-T1071 Residential 3/28/2009 9:55 23:46 Saturday MiniVol torn filter 

09-Q53 E.Tarmac 3/29/2009 9:00 24:44 Sunday 71 HiVol 

09-T1072 E.Tarmac 3/29/2009 8:39 24:32 Sunday 59 MiniVol 

09-T1073 E.Tarmac 3/29/2009 8:47 14:13 Sunday 88 MiniVol 11 p.m. shutoff 

09-T1074 W.Tarmac 3/29/2009 9:17 23:18 Sunday <detection 

limit 

MiniVol below minimum 

detection limit, which 

here is 3.2 ng/ m3

 at 

68% confidence level 

09-T1075 Residential 3/29/2009 9:38 23:13 Sunday 28 MiniVol 

09-T1076 Residential 3/29/2009 9:38 23:16 Sunday 37 MiniVol 

09-Q54 E.Tarmac 3/30/2009 9:51 23:25 Monday 44 HiVol 

09-T1077 E.Tarmac 3/30/2009 9:18 23:34 Monday 32 MiniVol 

09-T1078 E.Tarmac 3/30/2009 9:27 13:33 Monday 45 MiniVol 11 p.m. shutoff 

09-T1079 E.Tarmac 3/30/2009 9:31 23:28 Monday 26 MiniVol 

09-T1080 E.Tarmac 3/30/2009 9:34 23:28 Monday 26 MiniVol 

09-T1081 E.Tarmac 3/30/2009 9:37 23:26 Monday 34 MiniVol 

A total of 43 valid data samples were collected over a total of 8 different days. Most samples were 

measured using the MiniVols and in most cases were well above the detection limit. Only the West 

Tarmac location was frequently below the detection limit. Valid data from this study were used in the 

subsequent model-to-monitor comparison. Further details of the filter analysis can be found in 

Appendix A. 

Comparison of HiVols and MiniVols 

Data from the monitoring program was evaluated to determine if the sampling system was suitable for the 

model evaluation and if the summer program could make use of the same monitoring system. To 

determine the validity of the sampling system using the HiVol and MiniVol samplers, the following set of 

five questions were developed to characterize instrumentation-based uncertainty and to evaluate the 

suitability of using the MiniVol samplers in the summer program study. For each question the answer is 

provided based on the analysis of the monitored data. 

 9 
 

 

 

Question 1: What is the mean difference between the reference method (HiVol) and the MiniVol 

when comparing the collocated HiVol samplers (East Tarmac) and the MiniVols which sampled 

over the full 24-hour period? 

Answer 1: Figure 2-5a shows the results in graphic form for Question 1. These results show that 

the HiVol had a mean monitored concentration of 55 ng/m3

, which was about 72% higher than the 

mean collocated MiniVol concentration. The day-by-day comparison (Figure 2-5b) shows that 

this bias occurs on each day and is largest on days with the highest concentrations. 

 Question 1 - East Tarmac HiVol vs. MiniVol - Total 

54.5 

31.9 

0 

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

0 1 2 

HiVol MiniVol 

Lead Concentration ng/m3 

Question 1 - East Tarmac HiVol vs. MiniVol - Day 

Specific 

0 

20 

40 

60 

80 

100 

0 2 4 6 8 

Day 

Lead Concentration

ng/m3 

HiVol MiniVol 

Figure 2-5 a and b. Collocated HiVol versus MiniVol winter 

monitoring. 

Because of the significant low “bias” seen in the MiniVols relative to the FRM HiVol sampler, which 

used quartz filters, an examination of the field blanks was conducted by Chester LabNet to determine if a 

correction bias could be applied to the MiniVol Teflon filter samples. Based on an analysis of the 

laboratory reports (Appendix A) an average bias of -12.8 ng of lead per filter was found. If this correction 

 10 
 

 

 

bias is applied to all of the MiniVol samples and the measurement uncertainty3 is included, a revised 

comparison can be made between the HiVol and MiniVol samples. However, even after adjusting the 

results to account for the bias, an overall bias remains between the MiniVol and HiVol measurements. 

One potential explanation is the known tendency for the Teflon filters to have a static charge which will 

cause some larger particles not to adhere to the surface of the filter. 

Question 2: For March 12th and March 30th, when all samplers were located on the East Tarmac, 

what is the variability between the MiniVol’s measurements in comparison to the HiVol sampler? 

Answer 2: Figure 2-6 shows the results in graphic form for Question 2. This figure shows that 

on the two days when all of the instruments were collocated, the variability amongst the MiniVols 

is relatively small, twice the standard deviation of the three samples on each of the two days is 

less than ±35% of the mean value, and that the MiniVols are again biased low relative to the 

HiVol sampler. 

Question 2 - East Tarmac MiniVol Comparison 

14.3 

29.1 

24.6 

43.8 

0 

10 

20 

30 

40 

50 

0 1 2 

3/12 3/30 

Lead Concentration ng/m3 

MiniVol HiVol 

Figure 2-6. Collocated instruments at the East Tarmac (bars are 

twice the standard deviation). 

Question 3: What is the difference between Pb concentrations collected over the full 24-hour 

period and those collected during airport operation hours (7 a.m. to 11 p.m.)? Can 24-hour Pb 

concentrations be estimated reasonably well from samples collected during the 18-hour period 

during which the airport is open? 

Answer 3: Figures 2-7a-c show the results in graphic form for Question 3. We observed consistently 

higher Pb concentrations for samples collected over the 18-hours of airport operation compared with 

those collected for a full 24-hour day (Figure 2-7a). The 18-hour samples ranged from 16 ng/m3

 to 27.1 

ng/m3

 higher than the paired 24-hr samples. This difference is attributed to the piston-engine aircraft 

emissions during airport operation hours. To evaluate whether we can reasonably estimate a 24-hour 

concentration from an 18-hour sample, we compared the daily ratio of the 18-hour Pb concentrations with 

the 24-hour Pb concentrations and observed a range in these ratios (shown in Figure 2-7c) from 0.61 to 

0.69 (average 0.66). This average ratio is nearly identical to the ratio of the hours the samples were 

3

 This includes uncertainty from instrument calibration, counting statistics, peak overlap correction and absorption 

as reported by the laboratory. 

 11 
 

collected (18/24= 0.67). This implies that when the airport is closed, ambient Pb concentrations at the 

East Tarmac location return to background levels similar to those measured at the West Tarmac site (e.g., 

3-4 ng/m3

). This finding also suggests that monitoring for the summer program could be limited to airport 

operating hours and the resulting concentrations reasonably adjusted to estimate the 24-hour 

concentration. Another way to address the question would be to compare the mass of Pb from the 18-hour 

monitored sample with the mass of Pb from the paired 24-hour sample (Appendix A). 

Question 3 - East Tarmac Full Day vs. 11 p.m. Cut off 

of MiniVols 

31.9 

61.2 

0 

20 

40 

60 

80 

100 

120 

0 1 2 

Full Day 11 p.m. Cut off 

Lead Concentration ng/m3 

Question 3 - Daily Variation between 11 p.m. 

and Full Day MiniVols 

0 

20 

40 

60 

80 

100 

0 2 4 6 8 

Day 

Lead Concentration

ng/m3 

11 p.m. Full Day 

 12 
 

 

 

Quesiton 3 - Daily Mean Ratio of 11 p.m. 

Shutoff to 24-hr Intergrated Sample 

0.6 

0.62 

0.64 

0.66 

0.68 

0.7 

1 3 5 7 

Daily Ratio 

Figure 2-7. Full-day (24-hour) monitoring versus 18-hour4 monitoring. 

Question 4: Using the MiniVols, what are the prevailing upwind (West Tarmac) and downwind 

(East Tarmac) concentrations as well as the residential concentrations, paired in time? What is the 

gradient in the Pb concentration between the East Tarmac and residential (Clarkson) 

concentration (approximately 85 meters) and how does this inform the potential distance at which 

Pb concentrations return to urban background levels? 

Answer 4: Figure 2-8 shows the results in graphic form for Question 4. The results compare the day-byday upwind (West Tarmac) and downwind (East Tarmac) concentrations as well as the residential 

concentrations paired in time. With the exception of March 13th (Day 2), these results show that the 

residential monitor is always lower than the East Tarmac site. The differences between the East Tarmac 

and residential site are most pronounced on days with the highest ambient concentrations. On March 13th 

(Day 2), the sample in the residential monitor was not changed until 9:45 a.m. while the East Tarmac 

location sample was changed between 8:15 and 8:30 a.m. It may be possible that the residential monitor 

measured emissions during this intervening time period that were not captured on the East Tarmac filter. 

Based on this finding, March 13th was not recommended for the model-to-monitor comparison study. 

Figure 2-8 also shows that the average concentration gradient over the 85-meter distance between the East 

Tarmac and residential site is 16 ng/m3

. However, the residential site is more to the immediate east of the 

East Tarmac site rather than in a more northerly location that would place it in the more prevailing 

downwind direction. The gradient ranged from 27 to 7 ng/m3

, with the exception of March 13th for which 

the data were considered suspect. These results suggest it may be problematic to measure concentrations 

much beyond the residential site (Clarkson) using the MiniVols with their generally lower sample 

collection and biased measurements relative to the HiVols, except on days with high levels of general 

aviation activity. 

4

 The 18-hours coincided with the hours that the airport operates. 

 13 
 

 

 

 

Question 4 and 6 - Upwind vs Downwind vs
 

Residential Sites
 

0 

10 

20 

30 

40 

50 

60 

70 

Lead Concentrations

ng/m3 

0 2 4 6 8 10 

Day 

East Tarmac West Tarmac Residential 

Figure 2-8. Daily average lead concentrations at the three monitoring sites 

during the winter monitoring program. 

Question 5: For locations where the MiniVol samplers were collocated and collected for the 

same time period, what was the mean and mean difference? 

Answer 5: Figure 2-9 shows the results in graphic form for Question 5. These results compare 

the collocated MiniVol measurements collected for the same time period. This figure shows the 

mean and means difference (plotted as an error bar). Both the residential and East Tarmac sites 

showed small differences in 5 of the 6 periods and only on the day with the highest concentration 

did the mean difference exceed 10 ng/m3

. The West Tarmac site shows small differences in the 

mean and means difference owing to the very low observed concentration levels. 

Question 5 - Mean and Mean Difference for 

Individual Minivol Groups Collocated for the 

Same Time and Site. 

0 

20 

40 

60 

80 

0 1 2 3 4 5 

Num ber of Paired Days 

Mean Lead

Concentration

(ng/m3) with Mean

Difference 

1- E.Tarmac 5 - Residential 7- W.Tarmac 

Figure 2-9. Mean and mean difference (error bars) for collocated MiniVols. 

 14 
 

 

Implications for Summer Monitoring Program 

Based on the intercomparison between the HiVol and MiniVol measurements, two approaches were 

considered for the Summer Program: 

1. Retain the use of the MiniVols but minimize the differences with the HiVol by: 

	 Using an electrostatic charge eliminator for each Teflon filter prior to installation in a 

MiniVol; and 

	 Correcting the Teflon bias and improving accuracy with additional field blanks 

2. Use only HiVol instrumentation 

Option 2 was selected as the preferred approach for the Summer Monitoring Program because: 

1.	 Use of the HiVol samplers is consistent with the regulatory monitoring; 

2.	 A small but significant bias would remain with the use of the MiniVols, particularly at 

concentrations near the detection limit; 

3.	 The HiVol samplers would provide a better estimate of the off-airport spatial Pb concentration 

gradient and could be extended beyond the 85 meter distance; 

4.	 An adequate number of HiVol samplers were available from SCAQMD in support of the study. 

2.4 SUMMER MONITORING PROGRAM 

2.4.1 Approach 

The summer monitoring period extended over a one week period starting on Saturday, July 25th, through 

Friday, July 31st. During the summer period general aviation activity was similar on both weekdays and 

weekend days. Filter samples were changed out at approximately the same time on each of the days, with 

the operating parameters documented in logs (Appendix A). 

The decision to employ only HiVol samplers during the summer program required that electrical power 

be available for continuous use and introduced additional complications associated with site security and 

equipment footprint. As a result, the summer program used a new upwind monitoring location as well as 

two new additional residential locations. A total of four HiVol samplers were used during the 7-day 

summer monitoring program. Two of the HiVol samplers were provided by T&B Systems and two by the 

SCAQMD. 

The locations of the four monitors for the summer program are shown in Figure 2-10. The upwind site 

was adjacent to the airport maintenance5

 shed and is the same location that was used by SCAQMD in 

their earlier monitoring study (Fine, 2007). We used the same East Tarmac site that was used in the winter 

program, which is in the prevailing downwind direction from aircraft activity. 

Two residential locations in the prevailing downwind direction were used in this study. The site nearest 

the Airport is designated Residence 1 and is 100 meters from the East Tarmac site. This site used a 

backyard location with the sampler located near a wall but otherwise with good ambient exposure (Figure 

2-11). The residential site (Residence 2) is 175 meters from the East Tarmac site. The HiVol sampler was 

placed near the wall at the back of the property, but with the top of the inlet above the wall (Figure 2-12). 

5

 A new upwind site was used in the summer monitoring program due to the need for off the grid electrical power. 

 15 
The HiVol samplers were operated in the total suspended particulate (TSP) mode and were mostly 

operated only during airport operational hours to reduce the potential for noise complaints. The summer 

program also included one field blank sample that was carried through the process and analyzed. 

Appendix A contains measurements of all of the sample mass, Pb mass and blank measurements. 

Calibrations for all of the equipment were performed using certified flow standards. Pb samples were 

again analyzed by Chester LabNet using XRF and the filter media was quartz in an effort to minimize 

particle bounce. 

Source: GoogleEarth. 

Figure 2-10. Sampling locations during the Summer Monitoring Program: East Tarmac, Resident 1, 

Resident 2, and Maintenance Shed (M). 

 16 
 

 

 

 

Source: T&B Systems 

Figure 2-11. Location of the HiVol sampler at the Residence 1. 

Source: T&B Systems 

Figure 2-12. Location of the HiVol sampler at the 

Residence 2. 

2.4.2 Summer Program Monitoring Results 

Individual Monitoring Results 

Table 2-2 summarizes the ambient Pb air monitoring data collected during the summer monitoring 

program at Santa Monica Airport. The table shows the location of the monitor, the starting date, starting 

time and ending time, day of the week in which the sample was first collected, the type of monitor used to 

collect the data, and a description of any problems or invalid measurements (in the “Comments” column). 

A total of 28 valid data samples were collected over a total of 7 days. All samples were measured using 

HiVol samplers and in most cases were well above the detection limit. Only the Maintenance Shed 

location (which is located in the predominant upwind direction) showed concentrations below the 

detection limit. The highest monitored concentration was 79 ng/m3

, measured at Residence 1 on July 26th. 

Valid data from this study were used in the subsequent model-to-monitor comparison. Further details of 

the filter analysis can be found in Appendix A. 

Table 2-2. Pb Air Concentrations from Summer Monitoring Program at Santa Monica Airport 

Sample 

ID Site 

Start 

Date 

Start 

Time 

Duration 

(hh:mm) 

Day of 

Week 

Pb 

(ng/m3

) Comment 

09-Q539 East Tarmac 7/25/2009 8:16 24:29 Saturday 38 

09-Q540 Maint.Shed 7/25/2009 8:30 24:40 Saturday 2 Just above detection limit of 1.4 

ng/m3

 at 68% confidence 

09-Q541 Resident 1 7/25/2009 7:55 23:40 Saturday 44 

09-Q542 Resident 2 7/25/2009 8:02 18:28 Saturday 30 Shutoff at 2:30 a.m. 

09-Q543 East Tarmac 7/26/2009 8:53 23:07 Sunday 58 

09-Q544 Maint. Shed 7/26/2009 9:20 23:00 Sunday 4 

09-Q545 Resident 1 7/26/2009 7:40 15:20 Sunday 79 Shutoff at 11 p.m. 

09-Q546 Resident 2 7/26/2009 8:27 14:33 Sunday 45 Shutoff at 11 p.m. 

 17 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 2-2. Pb Air Concentrations from Summer Monitoring Program at Santa Monica Airport 

Sample 

ID Site 

Start 

Date 

Start 

Time 

Duration 

(hh:mm) 

Day of 

Week 

Pb 

(ng/m3

) Comment 

09-Q547 East Tarmac 7/27/2009 8:06 23:05 Monday 53 

09-Q548 Maint. Shed 7/27/2009 8:30 23:25 Monday 4 

09-Q549 Resident 1 7/27/2009 7:22 15:38 Monday 52 Shutoff at 11 p.m. 

09-Q550 Resident 2 7/27/2009 7:40 15:20 Monday 32 Shutoff at 11 p.m. 

09-Q551 East Tarmac 7/28/2009 7:20 24:25 Tuesday 62 

09-Q552 Maint. Shed 7/28/2009 8:05 23:20 Tuesday 4 

09-Q553 Resident 1 7/28/2009 6:42 16:18 Tuesday 76 Shutoff at 11 p.m. 

09-Q554 Resident 2 7/28/2009 7:00 Unknown Tuesday 50 Unknown sample duration - 

power lost 

09-Q555 East Tarmac 7/29/2009 7:52 23:28 Wednesday 55 

09-Q556 Maint. Shed 7/29/2009 7:30 24:10 Wednesday 6 

09-Q557 Resident 1 7/29/2009 6:47 23:57 Wednesday 32 

09-Q558 Resident 2 7/29/2009 7:08 23:53 Wednesday 23 

09-Q559 East Tarmac 7/30/2009 7:25 23:51 Thursday 34 

09-Q560 Maint. Shed 7/30/2009 7:46 24:51 Thursday < 

detection 

limit 

below detection limit of 1.4 ng/m3 

at 68% confidence 

09-Q561 Resident 1 7/30/2009 6:50 23:50 Thursday 27 

09-Q562 Resident 2 7/30/2009 7:06 16:09 Thursday 36 Shutoff at 11:15 p.m. 

09-Q563 East Tarmac 7/31/2009 7:24 24:55 Friday 45 

09-Q564 Maint. Shed 7/31/2009 7:45 24:18 Friday 3 

09-Q565 Resident 1 7/31/2009 6:46 24:49 Friday 39 

09-Q566 Resident 2 7/31/2009 7:04 16:04 Friday 42 Shutoff at 11 p.m. 

 18 
 

3 Soil and Dust Sampling 

The purposes of the soil and indoor dust Pb sampling were to explore the potential for a gradient in Pb 

concentrations in these media with distance from the airport and, as described in Chapter 4, to determine 

the re-entrained road dust Pb fraction in the vicinity of the Santa Monica Airport. The sampling program 

consisted of collecting soil and dust samples in locations at and near the Santa Monica Airport. 

3.1 SOIL SAMPLING 

3.1.1 Approach 

The soil sampling program was designed to gather data on the presence and distribution of total Pb in soil. 

Total Pb may be present in bulk soil samples (i.e., present throughout the soil matrix) or may be 

preferentially found in the fine-grained components of a bulk sample (sieved soil). It is the fine-grained 

components (clays and silts) of the soil that are potentially entrainable under certain wind and soil 

moisture conditions and thus subject to inhalation and ingestion by workers and residents in the 

surrounding area. Four sampling areas were selected based on: proximity to takeoff and landing areas, 

availability of relatively undisturbed and non-vegetated surficial earth materials, and accessibility. 

These four locations were: 

Area 1 – Clover Park: baseball fields and playground equipment adjacent to the aircraft 

parking and idling area near a historically contaminated industrial area.6 

Area 2 – Near runway 21 blast fence: maximum impact site for ambient lead from 

aircraft exhaust emissions. 

Area 3 – Prevailing upwind site. 

Area 4 – Neighborhood sampling: three homes located near the maximum neighborhood 

air impact sites (ranging from 55, 110 and 150 meters from the runway blast fence) and 

one home in the prevailing upwind area from the airport (1700 meters from the runway 

blast fence). Soil sampling in each home consisted of two samples total, one collected at 

the drip line to test for Pb from Pb-based exterior paint, and one sample collected in the 

yard. Additionally, two soil samples were collected near roadways: near the corner of 

Brookhaven Ave and Federal Ave and near the intersection of Ocean and Bundy. 

Sampling locations for the soil and dust (See Section 3.2) analysis for the north runway area and near 

roadway samples are shown in Figure 3-1. Sampling locations for Clover Park, the south runway area, 

and observation deck are shown in Figure 3-2. 

The choice of specific sample locations within these areas was dependent upon on a number of factors, 

including: accessibility, degree of disturbance (non-disturbed is best), degree of leaching from irrigation 

(samples were collected in areas least affected by irrigation water), vegetative cover (exposed soil is best), 

and soil type (predominantly fine-grained soil is best for collecting resuspended dust). 

6

 The Clover Park samples were taken before the summer 2009 construction began 

 19 
Near Road Samp

Soil: 53-120 mg/

Residence 1 

Soil: 26-49 mg/kg Dust: 684 ug/ft2 

Blast wall area 

Soil: 16-40 mg/kg 

Near Road Sample 

Soil: 32-77 mg/kg 

Blast Wall Area 

Dust: bdl 

Residence 2 

Soil: 130-150 mg/kg Dust: bdl 

Residence 3 

Soil: 12-47 mg/kg Dust (u): 93.6 ug/ft2 

Source: GoogleEarth. Figure 3-1. North runway area, nearby neighborhood, and near roadway soil and dust sample locations. 
Residence 4 

Dust (u): 64.8 ug/ft2 

Refueling Area 

Dust: bdl Residence 5 

Soil: 24-66 mg/kg Dust: bdl 

Upwind Sample 

Soil: 17-63 mg/kg 

Observati

Dust: bdl 

Clover Park Tot Lot 

Dust from rubberized surface: bdl Dust from stairs: bdl 

Adjacent to ball field stands 

Soil: 9.4-16 mg/kg 

Near fence adjacent taircraft parking area 

Soil: 17-35 mg/kg 

Source: GoogleEarth Figure 3-2. South runway, observation deck, and Clover Park soil sampling sites. 
 

Soil samples were collected using shovels, stainless steel hand trowels, and stainless steel mixing bowls. 

For each soil sample, we removed the top 2 inches of soil throughout a circular area with a diameter of 

approximately 18 inches (approximately 6 lbs of bulk soil was collected for each bulk sample). The 

excavated soil was placed in a stainless steel mixing bowl and mixed to blend the soil. Approximately 4 

oz of soil was placed in a laboratory-provided glass jar and labeled using a unique sample naming 

protocol. A subsample of the blended soil was removed for analysis of the bulk soil Pb concentration. The 

remainder of the blended sample was collected in a heavy duty plastic bag for submittal to the analysis 

laboratory for sieve processing using ASTM Method D1140. A minimum of 4 oz of soil passing through 

a #60 sieve was provided to the laboratory for analytical analysis. All sampling equipment was cleaned 

between sample locations using a mild detergent (tri-sodium phosphate or equivalent). 

The soil samples were submitted under chain-of-custody protocols to the State of California-certified 

analytical testing laboratory, Test America. Bulk soil samples were analyzed for a suite of metals 

including Pb by ICP-MS (EPA Methods 7471A/6020). The specific analyses for soil samples collected in 

each area are summarized below in Table 3-1. 

Table 3-1. Soil Sampling 

Area 

No. of Bulk 

Samples 

No. of Total 

Metal Analyses 

No. of Total Lead 

Analyses 

No. of Sieve 

Analyses for 

Pb 

Area 1 (Clover Park) 2 2 2 2 

Area 2 (Blast Fence) 1 1 1 1 

Area 3 (Upwind Site) 1 1 1 1 

Area 4 (Neighborhood)1

 10 10 10 10 

Totals 14 14 14 14 1 Three homes in the downwind neighborhood, one home in the upwind neighborhood, and two sites in 

the near roadway environment were sampled. Two bulk samples were collected at each home (one from 

the roof drip line and one from an area where dirt might be tracked into the house) and one bulk sample 

was collected at two separate roadways. Each bulk sample was analyzed for total metals. A sieve 

analysis was conducted on the bulk samples and the material passing a #60 sieve was analyzed for 

lead. 

3.1.2 Results 

Table 3-2 describes the sample ID, sampling locations, date of the collection, and type of soil sample 

collected. Table 3-3 reports the soil sampling results including the Pb concentration (mg/kg) as well as 

other metal concentrations for the bulk samples. 

Concentrations of soil Pb on airport property ranged from 16 to 63 mg/kg. Concentrations of Pb in soil 

collected at Clover Park ranged from 9.4 to 35 mg/kg. Concentrations of Pb in samples collected near 

roads ranged from 32 to 53 mg/kg with the sieved samples having Pb concentrations ranging from 77 to 

120 mg/kg. Residential soil samples had Pb concentrations ranging from 12 to 150 mg/kg in the bulk soil 

and 14 to 150 mg/kg in the sieved fraction. For comparison, the EPA standard for Pb in residential soil in 

play areas is 400 mg/kg and for non-play area soils 1,200 mg/kg (EPA, 2001). 

 22 
Table 3-2. Soil Sample Locations, Descriptions, and Types in the Vicinity of Santa Monica Airport 

Sample ID 

Collection 

Date 

Sample 

Type 

General 

Location Specific Location 

Area1SS1061209 6/12/2009 Bulk Soil Clover Park Near fence adjacent to aircraft parking area 

Area1SS2061209 6/12/2009 Bulk Soil Clover Park Adjacent to ball field spectator stands 

Area1WSBlank061209 6/12/2009 Blank Clover Park Not applicable 

Area1SS1061209 6/12/2009 Sieved Soil Clover Park Sieved sample from Area 1 location. 

Area1SS2061209 6/12/2009 Sieved Soil Clover Park Sieved sample from Area 2 location. 

NH1_SS072409 7/24/2009 Bulk Soil Neighborhood Near corner of Brookhaven Ave and Federal Ave. 

NH1_SS072409 7/24/2009 Sieved Soil Neighborhood Near corner of Brookhaven Ave and Federal Ave. 

NH2_SS072409 7/24/2009 Bulk Soil Neighborhood Residence 1 

NH2_SSDL072409 7/24/2009 

Bulk Soil -

Drip Line Neighborhood Residence 1 

NH2_SS072409 7/24/2009 Sieved Soil Neighborhood Residence 1 

NH2_SSDL072409 7/24/2009 Sieved Soil Neighborhood Residence 1 

NH3_SS072409 7/24/2009 Bulk Soil Neighborhood Residence 2 

NH3_SSDL072409 7/24/2009 

Bulk Soil -

Drip Line Neighborhood Residence 2 

NH3_SS072409 7/24/2009 Sieved Soil Neighborhood Residence 2 

NH3_SSDL072409 7/24/2009 Sieved Soil Neighborhood Residence 2 

NH4_SS072409 7/24/2009 Bulk Soil Neighborhood Residence 4 

NH4_SSDL072409 7/24/2009 

Bulk Soil -

Drip Line Neighborhood Residence 4 

NH4_SS072409 7/24/2009 Sieved Soil Neighborhood Residence 4 

NH4_SSDL072409 7/24/2009 Sieved Soil Neighborhood Residence 4 

NH5_SS072409 7/24/2009 Bulk Soil Neighborhood Residence 3 

NH5_SSDL072409 7/24/2009 

Bulk Soil -

Drip Line Neighborhood Residence 3 

NH5_SS072409 7/24/2009 Sieved Soil Neighborhood Residence 3 

NH5_SSDL072409 7/24/2009 Sieved Soil Neighborhood Residence 3 

NH6_SS072409 7/24/2009 Bulk Soil Neighborhood 

Roadway sample from planter at Bundy and 

Ocean Park 

NH6_SS072409 7/24/2009 Sieved Soil Neighborhood 

Roadway sample from planter at Bundy and 

Ocean Park 

FB_WS_072909 7/29/2009 Field Blank Airport Various 

2_BW_SS1072909 7/29/2009 Bulk Soil Airport 

Blast wall area - Blast wall dirt site – ~13ft along 

curve from left side of blast wall and ~17ft 

perpendicular to the curb into the field. 

2_BW_SS1072909 7/29/2009 Sieved Soil Airport 

Blast wall area - Blast wall dirt site – ~13ft along 

curve from left side of blast wall and ~17ft 

perpendicular to the curb into the field. 

3_UW_SS1072909 7/29/2009 Bulk Soil Airport 

Upwind area - ~44 ft from the curb where the 

bend in the road ends & 35 ft from tripod staked 

in dirt. Small sandy patch near some pieces of 

blacktop. 

3_UW_SS1072909 7/29/2009 Sieved Soil Airport 

Upwind area - ~44 ft from the curb where the 

bend in the road ends & 35 ft from tripod staked 

in dirt. Small sandy patch near some pieces of 

blacktop. 

NHBLANK_WSC073109 7/31/2009 Field Blank Neighborhood Various 

 23 
 

Table 3-3. Soil Sampling Metal Fractions Collected in the Vicinity of Santa Monica Airport (mg/kg) 

Sample 

Name 

Sample 

Date 

Soil 

Sample 

Type 

Metals by EPA Methods 7471A/6020 

MercuryAntimonyArsenic BariumBerylliumCadmiumChromiumCobalt Copper LeadMolybdenum NickelSelenium SilverThallium Vanadium Zinc 

Area1SS1061209 6/12/2009 Bulk 0.057 <1.0 1.6 110 <0.30 <0.50 14 3.6 12 17 <1.0 7.6 <1.0 <0.50 <0.50 18 250 

Area1SS2061209 6/12/2009 Bulk 0.068 <1.0 2.2 62 0.32 0.52 13 4.0 11 9.4 <1.0 8.9 <1.0 <0.50 <0.50 23 100 

Area1SS1061209 6/12/2009 Sieved NA NA NA NA NA NA NA NA NA 35 NA NA NA NA NA NA NA 

Area1SS2061209 6/12/2009 Sieved NA NA NA NA NA NA NA NA NA 16 NA NA NA NA NA NA NA 

NH1_SS072409 7/24/2009 Bulk 0.042 1.6 32 110 1.5 1.9 34 10 29 53 2.8 27 1.8 <0.50 1.6 54 160 

NH1_SS072409 7/24/2009 Sieved NA 1.1 21 120 0.45 1.5 45 9.4 41 120 2.4 29 <1.0 <0.50 <0.5 61 340 

NH2_SS072409 7/24/2009 Bulk 0.063 <1.0 12 130 0.45 0.75 33 7.4 30 38 1.8 24 <1.0 0.59 <0.50 48 85 

NH2_SSDL072409 7/24/2009 Bulk 0.033 <1.0 6.8 120 0.35 0.63 26 6.4 32 26 1.7 17 <1.0 <0.50 <0.50 37 100 

NH2_SS072409 7/24/2009 Sieved NA <1.0 18 170 0.64 0.56 48 9.5 43 49 2.5 32 <1.0 0.78 0.5 82 110 

NH2_SSDL072409 7/24/2009 Sieved NA 1.0 11 170 0.52 <0.50 51 9.0 57 45 2.5 28 1.0 <0.50 <0.50 64 140 

NH3_SS072409 7/24/2009 Bulk 0.085 <1.0 2.2 94 <0.30 <0.50 14 2.8 32 12 <1.0 6.8 <1.0 0.76 <0.50 18 74 

NH3_SSDL072409 7/24/2009 Bulk 0.12 <1.0 11 140 0.39 0.95 32 8.0 42 35 2.3 23 1.0 0.71 <0.50 47 250 

NH3_SS072409 7/24/2009 Sieved NA <1.0 2.3 61 <0.30 <0.50 21 4.6 28 14 <1.0 9.5 <1.0 0.93 <0.50 92 66 

NH3_SSDL072409 7/24/2009 Sieved NA 1.0 16 160 0.63 0.96 54 10 55 47 2.9 33 1.1 0.51 <0.50 81 770 

NH4_SS072409 7/24/2009 Bulk 0.036 <1.0 2.3 38 <0.30 <0.50 13 1.9 12 24 <1.0 4.7 <1.0 <0.50 <0.50 14 50 

NH4_SSDL072409 7/24/2009 Bulk 0.11 <1.0 1.1 45 <0.30 0.60 12 2.4 19 50 <1.0 5.7 <1.0 <0.50 <0.50 12 280 

NH4_SS072409 7/24/2009 Sieved NA <1.0 5.0 54 <0.30 <0.50 25 3.0 20 37 <1.0 8.1 <1.0 <0.50 <0.50 35 77 

NH4_SSDL072409 7/24/2009 Sieved NA <1.0 2.8 47 <0.30 <0.50 23 2.7 21 66 <1.0 7.1 <1.0 <0.50 <0.50 18 330 

NH5_SS072409 7/24/2009 Bulk 0.62 1.4 16 180 0.52 2.6 56 7.3 77 150 2.7 28 1.4 2.2 <0.50 45 240 

NH5_SSDL072409 7/24/2009 Bulk 0.097 1.3 21 110 0.38 1.1 37 7.7 46 130 2.5 26 <1.0 <0.50 <0.50 46 220 

NH5_SS072409 7/24/2009 Sieved NA 2.6 19 200 0.60 2.2 74 8.6 87 150 3.5 35 1.8 2.1 <0.50 65 260 

NH5_SSDL072409 7/24/2009 Sieved NA 1.8 26 120 0.47 0.67 46 8.1 47 150 2.9 29 1.0 <0.50 <0.50 55 220 

NH6_SS072409 7/24/2009 Bulk <0.020 <1.0 2.9 120 <0.30 <0.50 19 5.9 23 32 1.0 9.4 <1.0 <0.50 <0.50 32 120 

NH6_SS072409 7/24/2009 Sieved NA 3.2 6.5 140 <0.30 <0.50 33 6.3 57 77 3.5 18 <1.0 <0.50 <0.50 51 230 

2_BW_SS1072909 7/29/2009 Bulk NA <1.0 4.4 76 0.42 <0.50 21 5.1 13 16 <1.0 12 <1.0 <0.50 <0.50 37 37 

2_BW_SS1072909 7/29/2009 Sieved NA <1.0 6.4 120 0.48 <0.50 28 7.7 23 40 1.1 17 <1.0 <0.50 <0.50 51 57 

3_UW_SS1072909 7/29/2009 Bulk NA <1.0 3.4 110 0.33 0.69 24 4.9 25 17 <1.0 12 <1.0 1.2 <0.50 28 75 

3_UW_SS1072909 7/29/2009 Sieved NA <1.0 5.8 160 0.69 0.65 34 7.7 39 63 1.4 20 1.5 1.8 <0.50 48 140 

NOTE: 

NA = Not analyzed. 

3.2 DUST SAMPLING 

3.2.1 Approach 

Dust sampling was conducted on selected surfaces in each of the sample areas described above. Dust 

samples were collected by rubbing a laboratory-prepared absorbent material over a specified, measured 

area. The dust sample was then placed in a laboratory-provided glass jar. Dust sampling was conducted at 

several locations on or adjacent to the airport (in Areas 1, 2, and 37

) and at five homes in the vicinity of 

the airport as shown in Figures 3-1 and 3-2. 

Two types of dust samples were collected at the neighborhood homes: uncontrolled and controlled. 

Uncontrolled dust samples are samples collected from surfaces, typically windowsills, that were 

undisturbed and exposed to airborne matter prior to the start of this study. Uncontrolled dust samples 

were collected at Areas 1, 2, 3 and 4. Controlled dust samples are samples collected from surfaces which 

7

 Note that Area 3 for the dust sampling is not the same as Area 3 for the soil sampling; dust sampling Area 3 is at 

the refueling station 

 24 
had been pre-cleaned using water or isopropyl alcohol to remove residual material. These surfaces were 

then allowed to accumulate dust for approximately one week. Controlled dust samples were collected in 

Area 4. Table 3-4 shows the dust sample wipe locations and a description of the sample location. 

Table 3-4. Dust Sample Locations, Descriptions, and Types in the Vicinity of Santa Monica Airport 

Sample ID 

Collection 

Date 

Sample 

Type 

General 

Location Specific Location 

Area1WS1061209 6/12/2009 Wipe Clover Park From rubberized surface at Tot Lot 

Area1WS2061209 6/12/2009 Wipe Clover Park 

From corner of red stair (3rd from bottom) leading 

to platform 

NH2_WSJ072409 7/24/2009 

Wipe – 

Uncontrolled Neighborhood Residence 1– 1st floor west facing window sill 

NH2_WSC073109 7/31/2009 

Wipe – 

Controlled Neighborhood Residence 1– 1st floor west facing window sill 

NH3_WSJ072409 7/24/2009 

Wipe – 

Uncontrolled Neighborhood Residence 2– 1st f west facing window sill 

NH3_WSC073109 7/31/2009 

Wipe – 

Controlled Neighborhood Residence 2– 1st floor west facing window sill 

NH4_WSJ072409 7/24/2009 

Wipe – 

Uncontrolled Neighborhood Residence 4– 1st floor east facing window sill 

NH4_WSC073109 7/31/2009 

Wipe – 

Controlled Neighborhood Residence 4– 1st floor east facing window sill 

NH5 _WSJ072409 7/24/2009 

Wipe – 

Uncontrolled Neighborhood Residence 3- 2nd floor east facing window sill 

NH5_WSC073109 7/31/2009 

Wipe – 

Controlled Neighborhood Residence 3- 2nd floor east facing window sill 

NH7_WSJ072409 7/24/2009 Wipe Neighborhood Residence 5 – 2nd story south facing window sill 

2_BW_WS1072909 7/29/2009 Wipe Airport 

Blast wall area - 6th ridge down from the 1st 

large opening in the blast wall on the far left 

edge. 

3_RF_WS2073009 7/30/2009 Wipe Airport 

Refueling area - eastern corner post of the 

overhang of the refueling office. 

3_OD_WS1072909 7/29/2009 Wipe Airport 

Observation deck area - Second ‘T’ shaped 

connection to the left of the railing ending outside 

administration building. 

3_RF_WS1073009 7/30/2009 Wipe Airport 

Refueling area – in the middle of the hexagonal 

table near the office entrance. 

3_OD_WS2072909 7/29/2009 Wipe Airport 

Observation deck area - Centered above light to 

the right of the rightmost planter. 

2_BW_WS2072909 7/29/2009 Wipe Airport 

Blast wall area - behind 1st post in the guard rail 

along the road, last ridge on the lowest slat of 

wall. 

NH2_WSC073109 7/31/2009 

Wipe - 

Controlled Neighborhood Residence 1 – 1st floor west facing window sill 

NH3_WSC073109 7/31/2009 

Wipe - 

Controlled Neighborhood Residence 2 – 1st floor west facing window sill ( 

NH4_WSC073109 7/31/2009 

Wipe - 

Controlled Neighborhood Residence 4 – 1st floor east facing window sill 

NH5_WSC073109 7/31/2009 

Wipe - 

Controlled Neighborhood Residence 3 - 2nd floor east facing window sill 

NH7_WSC073109 7/31/2009 

Wipe - 

Controlled Neighborhood Residence 5 – 2nd story south facing window sill 

All dust samples (both controlled and uncontrolled) were analyzed by certified testing laboratory for a 

suite of metals following EPA Method 6020. A summary of the dust sampling program is provided in 

Table 3-5. 

 25 
 

 

 

Table 3-5. Dust Sampling Program 

Area No. of Dust Samples No. of Total Metal Analyses 

Area 1 (Clover Park) 2 2 

Area 2 (Blast Fence and Observation Deck) 4 4 

Area 3 (Refueling Station) 2 2 

Area 4 (Neighborhood) 10 10 

Totals 18 18 

3.2.2 Results 

Table 3-6 provides the results of Pb and other metal concentrations in dust wipe samples (in micrograms 

per square foot). Of the 18 dust samples, only three had Pb concentrations above the detection limit. The 

Pb concentration in these samples was 65, 94, and 684 μg/ft2

 at Residences 1, 3, and 5, respectively. All 

other controlled dust samples were less than the detection limit. For comparison, EPA’s standard for Pb in 

residential floor dust is 40 μg/ft2

 and for interior window sill dust it is 250 μg/ft2 (EPA, 2001). 

Table 3-6. Dust Sampling Measurements in micrograms per square foot in the Vicinity of Santa 

Monica Airport 

Sample 

Name 

Sample 

Date 

Sample 

Type 

Wipe 

Area 

Metals Results 

EPA Method 6020 

Units (micrograms per square foot) 

AntimonyArsenic Thallium BariumBerylliumCadmiumChromiumCobalt Copper LeadMolybdenum NickelSelenium SilverVanadium Zinc 

Area1WS 

1061209 6/12/2009 U 1 sq ft <2.0 <1.0 <1.0 <2.5 <0.50 <1.0 1.7 <1.0 <2.0 <1.0 <1.0 <1.0 <2.0 <1.0 <1.0 <20 

Area1WS 

2061209 6/12/2009 U 1 sq ft <2.0 <1.0 <1.0 <4.5 <0.50 <1.0 2.0 <1.0 <2.0 <1.0 <1.0 <1.0 <2.0 <1.0 <1.0 <20 

Area1WS 

BLANK061209 6/12/2009 Blank NA <72 <36 <36 <1.0 <0.50 <1.0 <1.0 <1.0 <2.0 <1.0 <1.0 <1.0 <2.0 <1.0 <1.0 <20 

NH2_WS 

J072409 7/24/2009 U 4 sq in 468 <36 <36 1440 <18 <1.0 234 <36 2088 684 72 130 <72 <36 101 3960 

NH2_WS 

C073109 7/31/2009 C 4 sq in <72 <36 <36 97 <18 <36 <72 <36 176 <36 <36 <36 <72 <36 43 <720 

NH3_WS 

J072409 7/24/2009 U 4 sq in 86 <36 <36 353 <18 <36 <72 <36 328 94 <36 <36 <72 <36 <36 2016 

NH3_WS 

C073109 7/31/2009 C 4 sq in <72 <36 <36 54 <18 <36 <72 <36 <72 <36 <36 <36 <72 <36 <36 <720 

NH4_WS 

J072409 7/24/2009 U 4 sq in <72 <36 <36 64.8 <18 <36 <72 <36 227 <36 <36 <36 <72 <36 <36 <720 

NH4_WS 

C073109 7/31/2009 C 4 sq in <72 <36 <36 36 <18 <36 <72 <36 <72 <36 <36 <36 <72 <36 <36 <720 

NH5_WS 

J072409 7/24/2009 U 4 sq in <72 <36 <36 83 <18 <36 <72 <36 <72 <36 <36 <36 <72 <36 <36 <720 

NH5_WS 

C073109 7/31/2009 C 4 sq in <72 <36 <36 47 <18 <36 <72 <36 <72 <36 <36 <36 <72 <36 <36 <720 

NH7_WS 

J072409 7/24/2009 U 4 sq in <72 <36 <36 292 <18 <36 75.6 <36 216 65 <36 <36 <72 <36 <36 828 

NH7_WS 

C073109 7/31/2009 C 4 sq in <72 <36 <36 54 <18 <36 <72 <36 <72 <36 <36 <36 <72 <36 <36 <720 

 26 
 

Table 3-6. Dust Sampling Measurements in micrograms per square foot in the Vicinity of Santa 

Monica Airport 

Sample 

Name 

Sample 

Date 

Sample 

Type 

Wipe 

Area 

Metals Results 

EPA Method 6020 

Units (micrograms per square foot) 

AntimonyArsenic Thallium BariumBerylliumCadmiumChromiumCobalt Copper LeadMolybdenum NickelSelenium SilverVanadium Zinc 

NHBLANK_ 

WSC073109 7/31/2009 Blank NA <72 <36 <36 <1.0 <0.50 <36 <72 <36 <72 <36 <36 <36 <72 <36 <36 <720 

2_BW_WS 

1072909 7/29/2009 U 4 sq in <72 <36 <36 36 <18 <36 <72 <36 <72 <36 <36 <36 <72 <36 <36 3420 

2_BW_WS 

2072909 7/29/2009 U 4 sq in <72 <36 <36 <47 <18 <36 54 <36 <72 <36 <36 <36 <72 <36 <36 2016 

3_RF_WS 

1073009 7/30/2009 U 4 sq in <72 <36 <36 <47 <18 <36 50.4 <36 <72 <36 <36 <36 <72 <36 <36 <720 

3_RF_WS 

2073009 7/30/2009 U 4 sq in <72 <36 <36 <47 <18 <36 <72 <36 <72 <36 <36 <36 <72 <36 <36 <720 

3_OD_WS 

1072909 7/29/2009 U 4 sq in <72 <36 <36 <47 <18 <36 <72 <36 <72 <36 <36 <36 <72 <36 <36 <720 

3_OD_WS 

2072909 7/29/2009 U 4 sq in <72 <36 <36 <47 <18 <36 50.4 <36 <72 <36 <36 <36 <72 <36 <36 <720 

FB_WS 

1072909 7/29/2009 Blank NA <72 <36 <36 <1.0 <0.50 <36 2.8 <36 <72 <36 <36 <36 <72 <36 <36 <720 

NOTES: 

U = Uncontrolled wipe sample; sample surface not cleaned prior to sampling 

C = Controlled wipe sample: sample surface cleaned allowed to accumulate dust for 1 week prior to sampling 

NA = Not applicable 

NH = Neighborhood sample 

RF = Airport refueling area 

BW = Airport blast wall 

OD = Airport observation deck 

1 Concentrations in table have not been converted to concentration per unit area 

 27 
THIS PAGE INTENTIONALLY LEFT BLANK. 

 28 
 

4 AIR QUALITY MODELING 

This chapter begins by presenting the methodology used in developing an emission inventory for aircraft 

Pb emissions (the principal source of Pb air emissions), and the procedures used to estimate emissions 

from other mobile and stationary sources. A discussion of the selection of the air quality model used in 

this study is presented along with the methods used to develop the air quality modeling inputs (including 

meteorology, terrain, land use, and background concentration). It concludes with a summary of the 

modeling results for the model-to-monitor comparison, the annual air quality modeling scenario, and a set 

of model sensitivity analyses. 

4.1 EMISSION INVENTORY 

4.1.1 Aircraft Sources 

For the scenarios examined in this analysis, the overall primary sources of Pb emissions to air are singleand multi-engine piston-powered fixed-wing aircraft using avgas and piston-engine helicopters. To 

accurately incorporate these emission sources into the air quality model and to track each mode of 

operation, aircraft activity was modeled separately for each mode and aircraft type. The fixed-wing modes 

include taxi, run-up, takeoff, climb, approach, and landing. The helicopter modes include taxi, climb, and 

landing. 

Data were assembled for this assessment from a variety of sources, including activity data provided by the 

Santa Monica Airport’s Operations Manager, fuel consumption information from FAA’s Emission 

Dispersion Modeling System (EDMS), and on-site survey data of general aviation activity collected as 

part of this study. 

Activity Data 

Two sets of aircraft activity data were needed for this analysis: an annual activity dataset and activity data 

for the two periods in which ambient monitoring data were collected (described in Chapter 2). The 

Airport only maintains records of the number of total operations8

, jet operations, and helicopter 

operations. Fixed-wing piston-engine aircraft activity was assumed to be the difference between the total 

operations less the jet and helicopter operations. 

Daily records of one year of aviation activity were provided by Santa Monica Airport’s Operations 

Manager, Stelios Makrides. At the time of the analysis, only January 2008 through November 2008 was 

available. When analyzing the 3-month seasonal averages for 2008, the winter season consisted of only 

January and February since December 2008 data were unavailable. 

For the 2009 model-to-monitor comparisons, Mr. Makrides provided day-specific counts for the periods: 

March 12th – March 17th, March 26th – March 31st, and July 25th – July 31st, as shown in Table 4-1. These 

observed activity data were used in the model-to-monitor comparisons and are typical activity levels, with 

the exception of July 26, 2009 (see explanation in Table 4-1). 

8

 “Operations” are the number of landings plus takeoffs. 

 29 
Table 4-1. Daily Aircraft Operations at Santa Monica Airport 

DATE Total Operations Jets Helicopter Propeller 

3/12/09 251 34 5 212 

3/13/09 352 48 8 296 

3/14/09 238 22 2 214 

3/15/09 319 34 2 283 

3/16/09 337 36 6 295 

3/17/09 464 48 2 414 

3/26/09 295 34 6 255 

3/27/09 453 54 18 381 

3/28/09 448 30 8 410 

3/29/09 347 42 1 304 

3/30/09 349 26 8 315 

3/31/09 422 36 8 378 

7/25/09 238 32 3 203 

7/26/091 153 50 7 96 

7/27/09 216 38 4 174 

7/28/09 409 32 6 371 

7/29/09 297 44 10 243 

7/30/09 251 30 20 201 

7/31/09 329 50 14 265 1 These anomalously low activity data for a Sunday were cross checked with 

the FAA’s ATADS Airport Operations database, which reported a total of 288 

operations for the same day, of which 7 were helicopters. These values were 

used in the monitor-to-model comparison assuming the typical jet aircraft 

fraction determined from other weekend days of 15% or 43 jets, 7 helicopters, 

and 238 fixed-wing aircraft. 

For the 2008 annual modeling scenario, the average daily activity data are summarized by season and 

weekday/weekend, as shown in Table 4-2. Propeller operations (i.e., piston-engine aircraft operations) are 

lowest in winter and there are only slight differences between weekdays and weekends. 

Table 4-2. Average Daily Aircraft Counts at Santa Monica Airport for 2008 

Season 

Total 

Operations 

Helicopter 

Operations 

Jet 

Operations 

Propeller 

Operations 

Weekday 

Dec- Feb 296.59 7.95 46.59 242.05 

Mar-May 364.80 10.41 53.14 301.25 

Jun-Aug 373.94 12.72 48.06 313.16 

Sep-Nov 368.52 7.57 44.77 316.18 

Weekend 

Dec- Feb 279.32 5.42 34.89 239.00 

Mar-May 355.36 7.46 39.82 308.07 

Jun-Aug 330.39 8.68 34.71 287.00 

Sep-Nov 287.60 7.00 35.93 244.67 

 30 
 

Based on interviews with Airport operational personnel, hourly activity levels were not well known. It 

was determined that this information could best be established by conducting an on-site survey focusing 

on activity levels for piston-engine aircraft. A similar study, but focused on jet aircraft, had been led a few 

years earlier at SMO by Professor Keith Mew, Department of Aviation and Administration, California 

State University, Los Angeles. Based on experience from his previous study, Dr. Mew led his team of 

graduate students in conducting a survey of piston-engine aircraft activity during two weekend periods in 

March 2009. A sample survey was performed for six days: March 13, 14 and 15, and March 27, 28 and 29 

for three periods: morning (8 a.m. and 10 a.m.), midday (10:30 a.m. and 1:30 p.m.), and afternoon (2 p.m. 

and 4 p.m.). These periods were selected based on discussions with SMO personnel, who indicated that 

these times typically covered the most active periods for piston-engine aircraft. 

The survey collected information on the number of takeoffs and landings as well as the time durations of 

the activities. For departure, data were collected for the following activities: apron to runway end, engine 

run-up, takeoff roll, and climb-out. For arrival, data were collected for: approach, landing, and taxi to 

apron (taxi-in). In addition, the following aircraft identification data were collected for each aircraft: tail 

fin number and number of engines (either single or multiple). 

The survey’s data on the temporal distribution based on activity level were the basis for establishing the 

diurnal activity level for aircraft emissions. However, because the survey did not cover all hours of the 

day, the diurnal profile estimated by SMO personnel was used to estimate the distribution for the 

remainder of the hours. Thus, the intraday activity levels were estimated by a combination of survey data 

and professional judgment. 

Figure 4-1 shows the piston-engine activity data collected on each survey day, the estimated distribution 

from an interview with SMO staff (ICF, 2008), and the final smoothed distribution used in the analysis 

(dark black line). This figure shows both a late morning peak and a secondary late afternoon peak in 

activity. This temporal profile was used in the modeling for the model-to-monitor comparison for the July 

2009 period and for the annual modeling. For the March model-to-monitor comparison, the hourly 

surveyed data were used. 

Time-in-mode data collected from the survey were used to determine the average length of time pistonengine aircraft were in specific modes of operation (i.e., taxi-out, run-up, takeoff, climb-out, approach, 

landing and taxi-in). Initial data were reviewed for outliers and corrections were made in consultation 

with Professor Mew. The final dataset was then used to determine average times-in-mode (TIM), which 

were used in calculating the aircraft Pb emissions for each mode. Table 4-3 shows the average time-inmode for each activity at the Airport. 

Fuel Consumption and Lead Concentration in Fuel 

Fuel consumption was the basis for determining the Pb emissions, as most of the Pb is exhausted through 

the tailpipe following fuel burning. Fuel consumption varies depending on the specific aircraft mode. 

EPA provided fuel consumption data on six different piston-engine aircraft (two multi- and four singleengine aircraft) in four different aircraft modes (taxi, takeoff, climb, and approach). These fuel 

consumption rates are the same as those contained in FAA’s EDMS model (FAA, 2009).9

 Because 

landing fuel consumption information was unavailable, it was assumed that landing fuel consumption was 

the same as takeoff. This is likely an overestimate, but the duration of this activity is relatively short. 

9

 Extracted from EDMS Version 5.0.2 - Emissions Inventory Report 

 31 
 

 

0.00% 

5.00% 

10.00% 

15.00% 

20.00% 

25.00% 

12:00 AM 3:00 AM 6:00 AM 9:00 AM 12:00 PM 3:00 PM 6:00 PM 9:00 PM 12:00 AM 

Percent of Day Piston-Engine Activity 

March 13th March 14th 

March 15th March 27th 

Marth 28th March 29th 

Average of All Days % from SMO personnel interview 

Figure 4-1. Hourly activity for piston-engine aircraft at Santa Monica Airport. 

Table 4-3. Average Time-in-mode for Fixed-wing Pistonengine Aircraft at Santa Monica Airport 

Mode Time 

Taxi To Runway 5 min 4 sec 

Run-up 1 min 29 sec 

Takeoff Roll 16 sec 

Climb-out 1 min 18 sec 

Approach 1 min 4 sec 

Landing 15 sec 

Taxi to Apron 2 min 17 sec 

Because EDMS does not include the run-up mode, the average fuel consumed during run-up was 

estimated based on fuel consumption data derived from engine operational manuals for four typical 

single-engine aircraft operating in the run-up mode.10 The average fuel consumption for these four 

engines was 7 gallons per hour. For the twin-engines, data from two aircraft operation manuals were 

used.11 These manuals reported average fuel consumption during engine run-up of 13 gallons per hour. 

10 Based on operation manual fuel flow curves for four single-engines (Lycoming IO360, Lycoming IO320, 

Lycoming GSO480 and TCM IO550) operating at recommended rpm. 11 Lycoming TIO-540-J2B2 and TCM TSIO550 

 32 
 

Average engine revolutions during run-up were 1,900 rpm. However, upon review of the site survey fleet 

data,12 it was determined that the simple average for the four typical single engines was not 

representative. The two most common engines at SMO are the Lycoming IO-360 and IO-320, which 

combined comprise 92% of the single engines. The weighted average of the fuel economy for those two 

engines provides a fuel consumption rate of 5.0 gallons per hour. This is about 28% lower than the simple 

four-aircraft average and was considered more representative of the single-engine run-up fuel 

consumption rate at SMO. Table 4-4 shows the final fuel consumption rates for each operational mode 

used in the SMO modeling. 

Table 4-4. Fuel Consumption Rate (g/s) within Each 

Operational Mode at SMO 

Single Engine Twin Engines 

Taxi Out 1.6 Taxi Out 5.1 

Takeoff 15.3 Takeoff 50.0 

Climb out 11.7 Climb out 38.8 

Approach 6.6 Approach 20.6 

Taxi in 1.6 Taxi in 5.1 

Run-up 3.8 Run-up 9.9 

Four helicopter piston-engines were used in EDMS 5.1 to estimate fuel consumption per LTO cycle. 

Table 4-5 lists the four types of helicopter engines and their Pb emission rate per LTO cycle, assuming a 

Pb concentration in avgas of 2.12 grams per gallon and a 5% engine retention rate.13 These four engine 

types were averaged and then allocated across time-in-mode as shown in Table 4-6. The operations 

manager at SMO estimated that about 25% of all helicopters have piston engines using avgas, therefore 

helicopter counts were multiplied by 0.25 to include only Pb-emitting-helicopters in the analysis. 

Table 4-5. Average Fuel Consumption for Helicopter Engine Type per LTO 

Helicopter Engine Type Fuel Consumed (g Pb/LTO) 

Robinson R22 IO-320-D1AD 5.55 

Robinson R22 IO-360-B 5.97 

Robinson R22 O-320 6.28 

Robinson R22 TSIO-360C 8.60 

Average 6.60 

Table 4-6. Helicopter Time-in-mode Estimates 

Mode Time 

Taxi Out 3 min 30 sec 

Climb 6 min 30 sec 

Approach 6 min 30 sec 

Taxi In 3 min 30 sec 

Total Time for LTO cycle 20 min 

12 The airport survey identified aircraft as single- or twin-engine in two ways. First, by visual observation of the 

aircraft and second by the tail number of the airplane. Tail numbers were cross-referenced with the FAA tail number 

database which provided engine type and number of engines. In cases where the two numbers did not match, the 

observed aircraft type was used as a default since tail numbers are sometimes reassigned. 13 The information used to develop this estimate is from the following references: Peterson (2008) and Rindlisbacher 

(2007). 

 33 
 

 

Emission Calculations 

Single- and multi- engine piston-powered aircraft emission rates were estimated based on the following 

equation for each individual operation mode: 

 fuel s Pb gal s modeCount  1 RetentionRate Emissionsg /s  s hr g gal

fuel/s = The amount (in grams) of fuel consumed per second in the 

particular operation mode. 

Pb/gal = Amount of Pb in grams per gallon of aviation fuel (2.12 

g/gal). 

s/mode = Average duration (in seconds) that the aircraft is the 

particular operation mode. 

g/gal = Weight of avgas fuel per gallon (2730.6 g/gal). 

Count = Number of aircraft type per hour. 

 RetentionRate = The fraction of Pb that is retained in the engine after the fuel 

is consumed (5%). 

s/hour = Number of seconds per hour (3,600). 

Helicopter emission rates were estimated based on the following equation for each individual operation 

mode: 

Pb emiss per LTOCount  1 RetentionRate FractionPiston Emissionsg s  s hr

Where: 

Pb emiss per LTO = Number of grams of Pb emitted over LTO cycle for a single 

helicopter. 

Count = Count of helicopters completing an LTO per hour. 

 Retention Rate = The fraction of Pb that is retained in the engine after the fuel 

is consumed (5%). 

 FractionPiston = Percentage of total helicopters that have piston engines 

(25%).

 s/hour = Number of seconds per hour (3,600). 

Emission Totals 

Tables 4-7 and 4-8 present the Pb emissions by aircraft type and mode, respectively. These figures show 

that single-engine aircraft dominate the Pb emissions at SMO and that climb-out and approach modes 

account for nearly half of Pb emissions. However, as will be discussed later in this chapter, these two 

sources are relatively minor contributors to the maximum downwind Pb concentration. 

 34 
 

Table 4-7. Pb Emissions (kg/yr) by Aircraft Type (2008) at SMO 

Aircraft Type Lead Emissions (%) 

Single 107.5 (90.7) 

Multi 8.5 (7.2) 

Helicopter 2.6 (2.2) 

Table 4-8. Pb Emissions (kg/yr) by Aircraft Mode (2008) at SMO 

Mode Lead Emissions (%) 

Taxi To Runway 20.4 (17.6) 

Run-up 13.5 (11.4) 

Takeoff Roll 10.0 (8.4) 

Climb-out 37.9 (32.7) 

Approach 17.9 (15.8) 

Landing 9.4 (7.9) 

Taxi to Apron 9.5 (8.4) 

Source Locations 

The horizontal and vertical locations of the single- and multi-engine piston-powered aircraft emissions 

used in this study were based on Santa Monica Airport’s Fly Neighborly Program, which identifies the 

preferred fixed-wing operational departure and arrival pathways 

(http://www01.smgov.net/airport/n_fixedwing.aspx ). The flight pathway is the same as was used in the 

Report on the Generation and Downwind Extent of Emissions Generated From Aircraft and Ground 

Support Operations (Piazza, 1999). Likewise, the location of helicopter emissions were developed based 

on the description provided in Santa Monica Airport’s Fly Neighborly Program, which also identifies the 

preferred helicopter operational departure and arrival pathways 

(http://www01.smgov.net/airport/n_helicopter.aspx ). These flight paths were divided into a discrete 

number of source locations for modeling. 

Table 4-9 provides summary information on each mode for each aircraft type, including the number of 

source locations per mode and the altitude range during the mode. Figure 4-2 shows the horizontal 

location of each discrete emissions source per aircraft type and per mode. In the key in Figure 4-2, 

“Airplane” corresponds to both single- and multi-engine piston-powered aircraft. Figures 4-3 and 4-4 

show the aircraft positions in a three-dimensional illustration from the perspective of a few hundred 

meters above the ground. Figure 4-3 faces eastward and Figure 4-4 faces westward, with neither 

differentiating between mode and aircraft type. 

Table 4-9. Details on the Emission Source Positions for Each Mode of Each Aircraft Type 

Aircraft 

Type Mode 

Number of 

Source 

Locations 

Highest 

Point 

(m) 

Lowest 

Point 

(m) Description and Notes 

Pistonengine Taxi 33 1 1 

Piston-engine aircraft are assumed to travel the full length of 

the taxiway. Single-engine aircraft approach only from the 

south taxiway. Multi-engine aircraft use the north and south 

taxiways equally. 

Pistonengine Run-up 1 1 1 Run-up is at the north end of runway. 

 35 
 

Table 4-9. Details on the Emission Source Positions for Each Mode of Each Aircraft Type 

Aircraft 

Type Mode 

Number of 

Source 

Locations 

Highest 

Point 

(m) 

Lowest 

Point 

(m) Description and Notes 

Pistonengine Takeoff 31 113.7 1 

Takeoff corresponds to the initial roll down about half the 

runway and then the aircraft’s initial lift off of the ground until 

reaching the south end of the runway. 

Pistonengine Climb 11 182 118.4 Climb corresponds to the aircraft’s position through about 

the first 0.5 km beyond the south end of the runway. 

Pistonengine Approach 37 145.8 39.24 Approach is from the northeast. 

Pistonengine Landing 31 21.8 1 Landing begins at the north end of the runway. 

Helicopter Taxi 33 1 1 Helicopters are assumed to use half the length of a taxiway. 

The north and south taxiways are used equally. 

Helicopter Climb 34 232.88 1 

Helicopter departures begin halfway down the runway and 

are towards the south end of the runway. Helicopters then 

turn left (southward) at the end of the runway to fly over the 

Penmar Golf Course. 

Helicopter Landing 45 274.5 0 

Landing begins above the north or south taxiway. 

Helicopters execute a 270-degree descending turn over the 

taxiway. The north and south taxiways are used equally. 

Figure 4-2. Location of each emissions source for each mode by type of aircraft. 

 36 
Source: GoogleEarth background. 

Figure 4-3. The Horizontal and vertical positions of emissions from fixed wing aircraft and helicopteris towards the east). 
Source: GoogleEarth background. 

Figure 4-4. The Horizontal and vertical positions of emissions from fixed wing aircraft and helicopteris towards the west). 
 

4.1.2 On-road Sources 

Gasoline and diesel fuel contain small quantities of naturally occurring Pb (~ 0.00005 g/L in gasoline 

[EPA 2006]). To accurately include these emissions in the air modeling impact assessment, roadways in 

close proximity to the airport were explicitly modeled. Other on-road mobile source emissions (e.g., 

resuspended road dust) were included as general area source emissions. The Pb emissions from gasoline 

and diesel vehicles for the three major arterials surrounding the airport that were explicitly included in the 

analysis are shown in Figure 4-5, and are described as follows: 

 23rd Street (from Ocean Park Blvd. to Rose St.); 

 Ocean Park Blvd. (from 30th St. to South Bundy Dr.); and 

 Bundy Dr. (from Ocean Park Blvd. to Airport Ave.). 

Daily traffic counts with hourly resolution for Ocean Park Blvd. and 23rd Street were provided by the City 

of Santa Monica. The most recent traffic counts for these two roads were made in 2003. We used U.S. 

census population data14 from 2000 to 2007 to project traffic changes for 2008 assuming traffic growth 

increased linearly with population growth. The population in Santa Monica between 2000 and 2007 only 

increased by 3,000 people, or 3.6%. Traffic data for South Bundy came from the City of Los Angeles15 as 

this roadway is just outside the Santa Monica city limits. The most recent traffic counts available for 

South Bundy Dr. were for National Blvd. at South Bundy and were collected on November 18, 2003. As 

with the other two roadways, the traffic data were linearly scaled with Santa Monica population16 to 

estimate traffic volumes in 2008. Table 4-10 provides the statistics on each road, including length, area, 

traffic count, and the year the traffic counts were collected. 

The traffic counts did not include estimates on the fleet traffic mix (light duty automobiles, trucks and 

buses). An estimate of these fractions was obtained as follows. Bus data were retrieved from Santa 

Monica’s Big Blue Bus system.17 The system-wide map of bus routes was reviewed and only buses that 

travel on Ocean Park Blvd., South Bundy Dr., and 23rd St. were analyzed. Only bus routes 6, 8, and 14 

travel on either Ocean Park Blvd., South Bundy Dr. or both. No buses were found to travel on 23rd St. The 

bus schedules were reviewed to estimate the number of buses per hour that traveled on each road. Santa 

Monica has a large fraction (43%) of buses operating with liquefied petroleum gas (LPG) that do not emit 

Pb. It was assumed that 43% of the buses traveling along Bundy and Ocean Park were fueled with LPG. 

Table 4-11 lists the total number of daily bus trips operating on Bundy and Ocean Park per weekday and 

weekend. An additional 5% of the traffic operating on these major arterials was assumed to be diesel 

fueled trucks. 

14 U.S. Census Bureau Population Trends: Santa Monica City, CA. Visited March 23, 2008. 

http://factfinder.census.gov/servlet/SAFFPopulation?_event=ChangeGeoContext&geo_id=16000US0670000&_geo 

Context=01000US%7C04000US06%7C16000US0670000&_street=&_county=santa+monica%2C+CA&_cityTown 

=santa+monica%2C+CA&_state=&_zip=&_lang=en&_sse=on&ActiveGeoDiv=geoSelect&_useEV=&pctxt=fph& 

pgsl=010&_submenuId=population_0&ds_name=null&_ci_nbr=null&qr_name=null®=null%3Anull&_keyword 

=&_industry= 15 http://ladot.lacity.org/tf_hist_auto_counts.htm 16 Santa Monica population data was used as the change in traffic along this roadway is more affected by Santa 

Monica population changes than the City of Los Angels which encompasses a population spread over an area of 470 

square miles. 

17 http://www.bigbluebus.com/home/index.asp 

 39 
Source: GoogleEarth. 

Figure 4-5. Major roadways in close proximity to Santa Monica Airport explicitly modeled in AERMO
 

 

 

Table 4-10. Traffic Counts for the Three Major Roadways near 

Santa Monica Airport 

Street 

Length of 

Road (m) 

Area of 

Road (m2

) 

Daily 

Count 

Year of 

Count 

23rd St. 1,046 11,842 23,958 2003 

Ocean Boulevard 853 17,343 31,295 1998 

Bundy Dr. 821 16,803 17,700 2003 

Table 4-11. Daily Bus Trips on Major Roadways 

near Santa Monica Airport 

Street Weekday Saturday Sunday 

Bundy Dr. 68 46 32 

Ocean Park Blvd. 74 39 39 

Emission Calculations 

Each roadway source’s emissions were determined as follows: 

2 Emissions g s g s sec m  
 

Count08VehType Veh%VehTyp  Len  EFVehTyp  HrFrac  hr
 3600s  g 1000mg

VehType 

Area 

Where: 

Count08VehType = The 2008 total traffic count for vehicle type, VehType 

Veh%VehType = Fraction of vehicle count comprised of vehicle type, VehType. 

Diesel trucks accounted for 5% of vehicles. The percentage of 

vehicles that were diesel buses depended on the street, and was 

calculated by dividing the daily total vehicle count (Table 4-10) by 

the daily total bus count (in Table 4-11) assuming 57% were diesel 

fueled. The percentage of vehicles that were gasoline fueled 

vehicles was determined by (100% - 5% trucks - X% buses). 

Len = Length of roadway (mile) 

EFVehType = Emission factor, in mg Pb per mile of roadway, for vehicle type, 

VehType. The hot stabilized summer emission factor of 0.002 mg 

of Pb/mile was used for gasoline vehicles (EPA, 2006; Table 2-19 

as obtained from Cadle et al. (1999) from dynamometer testing of 

in-use, light-duty vehicles model years 1991-1996). The emission 

factor for diesel fueled truck and bus engines was 0.00724 mg/mile 

(EPA, 2006; Table 2-20 based on extensive profiles of diesel 

emissions as developed by Lowenthal et al. [1994]) 

HrFrac = The fraction of daily traffic activity per hour of the day, averaged 

across all three roads. These fractions are shown graphically in 

Figure 4-6. An average distribution was used to lessen the bias 

from the single day of sampling. 

Area = The area of each roadway (square meters). 

 41 
A v erag e P erc e nt o f T r a f f i c 

0% 

2% 

4% 

6% 

8% 

10 % 

12:00 AM 

2:00 AM 

4:00 AM 

6:00 AM 

8:00 AM 

10:00 AM 

12:00 PM 

2:00 PM 

4:00 PM 

6:00 PM 

8:00 PM 

10:00 PM 

Time of Day 

Percent of Daily Traffic 

Figure 4-6. Hourly distribution of traffic on three major 

roadways surrounding Santa Monica Airport. 

4.1.3 Area Source Emissions 

The area source emission inventory for non-aircraft sources was developed based on the emission 

inventory previously prepared by SCAQMD and the California Air Resources Board (CARB) for the 

Multiple Air Toxics Exposure Study III (MATES-III) (SCAQMD, 2008). These emissions include all 

mobile source emissions not discussed in the preceding sections (e.g., brake and tire wear, re-entrained 

road dust), and all other types of non-road sources (e.g., construction dust, locomotives, fuel combustion, 

cooking). MATES-III started with a 2002 baseline emissions (as used in the 2007 Air Quality 

Management Plan [AQMP]) and was updated to 2005, which was the central year analyzed in MATESIII. Emissions specific to source categories (or Source Classification Codes, SCCs) and to distinct 2x2-km 

grids were developed for the following criteria pollutants and for total organic and total suspended 

particulates. Pollutant groups speciation were based on the CARB speciation profiles: 

 Carbon monoxide; 

 Nitrogen oxides; 

 Sulfur oxides; 

 Total organic gases; 

 Total suspended particulates; 

 Particulate matter, 10 micrometers and smaller (PM10); and 

 Particulate matter, 2.5 micrometers and smaller (PM2.5). 

The source categories and source classification codes (SCCs) analyzed were part of three larger groups of 

area sources: non-mobile area sources, on-road mobile sources (in two groups: heavy-duty vehicles and 

light- and medium-duty vehicles), and off-road mobile sources. For each of the non-mobile categories, a 

category-specific methodology was used by SCAQMD to derive the criteria pollutant emissions. For onroad mobile sources, emission factors from CARB’s EMFAC2007 (v2.3) were coupled with traffic 

activity data from the regional transportation modeling performed by the Southern California Association 

of Governments (SCAG). The coupling of emission factors (g/mile) and traffic activity data (vehicle 

miles traveled) was done using the Caltrans’ Direct Travel Impact Model (DTIM) to generate hourly 

gridded emissions. For off-road mobile sources, we used CARB’s OFF-ROAD model, which incorporates 

regulations, technology types, seasonal conditions, equipment population, equipment activity, horsepower 

and load factors, and emissions factors to produce annual emissions. The annual emissions were scaled to 

seasonal emissions using spatial and temporal features of the various area grids. This analysis excluded 

 42 
 

from the SCAQMD area source inventory the off-road emissions from aircraft using leaded aviation fuel, 

as these emissions were already developed as described in the previous sections. 

Nine 2x2-km area source grids from the SCAQMD air emission inventory centered approximately on the 

Santa Monica Airport were used to estimate the area source emissions in the vicinity of Santa Monica 

Airport. The SCAQMD 2x2 km emission inventory of annual PM10 emissions was then used for each 

source category or source classification code within each grid in combination with speciation profiles to 

estimate the area source Pb emissions. Speciation profiles were based on several sources as shown in 

Table 4-12. The paved road dust and engine exhaust are, to a small degree, a double counting of the onroad emissions as included for 23rd Street, Ocean Blvd and Bundy, however the emissions here are 

distributed over an area of 4 square kilometers and the three additional streets explicitly included 

represent an increase of less than 0.1 in Pb emissions. 

Table 4-12. Pb Emission Factors For Selected Area Sources 

Source Type Weight Percent of PM10 Weight Percent of PM2.5 

Unpaved road dust1 0.013 0.013 

Cooking1 0.0015 0.0014 

Construction dust1 0.07 0.083 

Paved road dust2 0.0077 0.0077 

Gasoline engine exhaust3 0.016 0.016 

Diesel engine exhaust3 0.016 0.016 

Locomotive4 0.03 0.03 

Commercial Ships4 0.03 0.03 1 General speciation profiles CARB (2002) 2 Site-specific road-side soil samples measured in July 2009 at the northern corner of the airport (Bundy Dr. and 

Ocean Park Boulevard) 3 Health Effects Institute (HEI) Tunnel Study (HEI, 2006) 4 EPA supplied information 

SCAQMD also provided cycle codes to partition the annual emissions to either: (1) each month, day of 

the week, and hour of the day (for non-mobile and off-road sources), or (2) each hour of the day (for onroad emissions). The SCAQMD SCC code for the entrained road dust category for paved roadway 

indicated a flat diurnal profile. This profile was replaced with the diurnal profile for light- and mediumduty vehicles as entrained road dust from paved roadways is expected to be closely related to vehicle 

activity levels. 

All area source categories combined accounted for approximately 67 kg/year of Pb across all nine area 

source grid cells. The total Pb emissions across all area source types (except piston-fired aircraft) for each 

Level 1 and Level 2 source classification code are presented in Table 4-13. Entrained road dust sources 

dominate the collective area source emissions when piston-fired aircraft are excluded, with a total of 41 

kg/year of Pb spread over the 36 square kilometer area. By comparison, the Santa Monica airport pistonfired aircraft emissions (exclusive of climb-out and approach) total about 53 kg/year over an area of just 

one square kilometer. The following three groups of categories together account for another 26% of the 

total area source Pb emissions: 

	 Dust from construction and demolition activities accounts for about 6.6 kg/year of Pb (about 10% 

of the total area source Pb emissions); 

	 Diesel and gasoline PM from exhaust emissions from on-road vehicles account for about 5.7 

kg/year of Pb (about 9% of the total area source Pb emissions); and 

	 Cooking activities account for about 5.2 kg/year of Pb (about 7% of the total area source Pb 

emissions). 

 43 
Table 4-13. Total Area Source Pb Emissions, Across All Nine Area Source Grids 

Source Classification Code 

Level 1 Description 

Source Classification Code 

Level 2 Description 

Total Pb 

Emissions 

(kg/year) 

Paved Road Travel Entrained Road Dust 38.5 

Cooking Commercial Charbroiling 4.22 

Construction And Demolition Building Construction Dust- Commercial 3.40 

Paved Road Travel Diesel PM [tailpipe exhaust emissions] 3.18 

Unpaved Road Travel Entrained Road Dust 2.70 

Paved Road Travel Gasoline PM [tailpipe exhaust emissions] 2.49 

Construction And Demolition Construction And Mining Equipment 1.93 

Construction And Demolition Building Construction Dust - Institutional 1.79 

Paved Road Travel All Brake Wear 1.39 

Construction And Demolition Building Construction Dust - Residential 1.39 

Cooking Cooking (Unspecified) 1.02 

Paved Road Travel All Tire Wear 9.84E-01 

Construction And Demolition Building Construction Dust- Industrial 5.40E-01 

Service And Commercial Other 3.02E-01 

Service And Commercial Transport Refrigeration Units 2.91E-01 

Service And Commercial Road Construction Dust 2.85E-01 

Service And Commercial Production 2.77E-01 

Mineral Processes Grinding/Crushing 1.91E-01 

Mineral Processes Fuel Combustion - Water Heating 1.82E-01 

Mineral Processes Fuel Combustion - Space Heating 1.81E-01 

Mineral Processes Commercial 9.62E-02 

Unplanned Fires Automobile Fires 9.53E-02 

Trains Locomotives 7.30E-02 

Trains Other 7.08E-02 

Trains Lawn And Garden (Commercial) 6.99E-02 

Trains Other 6.67E-02 

Other (Fuel Combustion) I.C. Reciprocating Engines 5.58E-02 

Other (Fuel Combustion) Lawn And Garden (Residential) 5.08E-02 

Other (Fuel Combustion) Dust From Unpaved Roads And Associated Areas 4.81E-02 

Other (Fuel Combustion) Structural Fires 4.49E-02 

Other (Fuel Combustion) Commercial (Residential) 3.73E-02 

Residential Fuel Combustion Fuel Combustion - Cooking 3.73E-02 

Residential Fuel Combustion Lawn And Garden (Other) 3.52E-02 

Residential Fuel Combustion Manufacturing 3.12E-02 

Residential Fuel Combustion Space Heating 3.05E-02 

Residential Fuel Combustion Water Heating 2.93E-02 

Residential Fuel Combustion Surface Blasting 2.82E-02 

Fugitive Windblown Dust Dust From Pasture Lands 2.10E-02 

Metal Processes Secondary Production 1.21E-02 

Manufacturing And Industrial I.C. Reciprocating Engines 1.21E-02 

Manufacturing And Industrial Sand And Gravel Excavation And Processing 8.48E-03 

Manufacturing And Industrial Metrolink 5.81E-03 

Manufacturing And Industrial Other 5.72E-03 

Manufacturing And Industrial Other 4.72E-03 

Manufacturing And Industrial Commercial (Other) 4.01E-03 

Off-Road Equipment Airport Ground Support Equipment 3.13E-03 

Fuel Combustion Other 1.83E-03 

Fuel Combustion Trains 1.26E-03 

 44 
 

Table 4-13. Total Area Source Pb Emissions, Across All Nine Area Source Grids 

Source Classification Code 

Level 1 Description 

Source Classification Code 

Level 2 Description 

Total Pb 

Emissions 

(kg/year) 

Fuel Combustion Military Tactical Support Equipment 1.04E-03 

Fuel Combustion Other 2.53E-04 

Fuel Combustion Resource Recovery 3.93E-05 

Fuel Combustion Entertainment 2.81E-05 

4.1.4 Point Source Emissions 

Point sources of Pb include18 sources such as Pb battery recyclers and battery manufacturers, Pb smelters, 

waste incineration, metal industries and glass manufacturers. The SCAQMD maintains an emission 

inventory based on a permit inventory for point source facilities throughout the district. SCAQMD 

provided the location, source code, operation frequencies, and Pb emissions information for 566 point 

source facilities within the South Coast Air Basin. These point source locations and emissions are 

representative of the year 2006, and it was assumed that these data were also representative of 2008. Pb 

emissions for each facility were provided by SCAQMD at the source category code (SCC) level. Some 

facilities reported multiple SCCs associated with Pb emissions. 

Initially, we proposed modeling all point sources within a 20 km radius of SMO. The 86 Pb-emitting 

point source facilities within 20 km of the airport emitted a total of 27.5 kg/year of Pb. However, a 

number of facilities emitting relatively large amounts of Pb were located just outside this radius. These 

additional facilities emitted a total 1,877.8 kg/year of Pb (see Figure 4-7) and were dominated by a single 

facility (Exide Technologies – a Pb-acid battery recycling plant as shown on Figure 4-7) that emitted 

1,813.5 kg/year Pb. In order to include these substantial Pb emissions in the model, all 144 Pb-emitting 

point sources within a 25 km radius of the airport were included in the air quality modeling. The Exide 

Technologies facility and the seven other facilities that together make up 99.5% of the point-source Pb 

emissions within 25 km of the airport are shown in Table 4-14. Appendix B shows more details on each 

Pb-emitting SCC at each of the 144 lead-emitting point sources. 

Data on physical stack parameters (stack height, diameter, exit gas temperature, and exit gas velocity) are 

needed to model each Pb emissions point source. While SCAQMD was not able to provide any physical 

stack parameters as part of their permit inventory, point source facilities can voluntarily report emissions, 

stack, and process information at the pollutant-level to the EPA’s National Emissions Inventory (NEI). 

However, some of the facilities provided by SCAQMD could not be found in the NEI. In these cases, 

emissions data from SCAQMD were used and physical stack parameters were estimated based on 

parameters provided in the NEI for similar facilities and processes. 

The facilities provided by SCAQMD were manually cross-referenced to the facilities contained in the 

2002 EPA National Emissions Inventory (NEI) Version 3. Though the 2005 NEI is the most current NEI 

available, it was in its early stages of development at the time of analysis (early 2009) and evolving 

quickly. The 2002 NEI was selected because it was likely a more quality-assured and stable dataset. In 

order to account for possible geographic coordinate discrepancies between facilities in both the 

SCAQMD and the NEI, all Pb-emitting facilities in the 2002 NEI Version 3 that were within 27 km of the 

airport were manually matched to the facilities provided by SCAQMD that were within 25 km of the 

airport. The facility matching was based on facility coordinates, facility name, and facility address. 

18 Many other source types are located at fixed locations, but are not significant enough in terms of emissions that 

they are listed as point sources. 

 45 
 

Figure 4-7. Point source facilities emitting Pb near Santa Monica Airport. (Larger circles and warmer 

colors reflect greater Pb emissions.) 

Table 4-14. Facilities that Comprise 99.5% of Point Source Pb Emissions Within 25 km of SMO 

Facility Name Facility City 

FacilityAverage 

Latitude 

(UTM 11N) 

FacilityAverage 

Longitude 

(UTM 11N) 

Lead 

Emissions 

(kg/year) 

Cumulative 

Percentage 

Lead 

Emissions 

Exide Technologies Los Angeles 3763256 389792 1,813.5 95.2% 

Owens-Brockway Glass Container Inc Vernon 3761510 388230 27.7 96.6% 

Liberty Mfg Inc Los Angeles 3764900 386169 19.1 97.6% 

Chevron Products Co. El Segundo 3753601 368842 10.4 98.2% 

Glendale City, Glendale Water & Power Glendale 3780120 382110 10.3 98.7% 

Chevron Products Co. El Segundo 3753601 368842 8.1 99.1% 

The Strelitz Co Inc Los Angeles 3761559 382680 3.9 99.4% 

U S Radiator Corporation Vernon 3762592 389333 2.8 99.5% 

 46 
 

 

Among the 144 SCAQMD Pb-emitting facilities within 25 km of the airport, 22 facilities were matched to 

facilities in the NEI. Some of the 117 SCAQMD facilities not matched to the NEI may actually be in the 

NEI, but the facility data presented in each database were not consistent enough to make a match without 

further information. For each of the 22 Pb-emitting point source facilities provided by SCAQMD that 

were manually matched to the Pb-emitting point source facilities in the NEI, the physical stack parameters 

of all Pb-emitting sources at the facility were averaged together.19 These facility-level averaged physical 

stack parameters were then used in the air quality modeling. 

For facilities not matched to the NEI, each SCC associated with Pb emissions at a facility was crossreferenced to the “Stack Parameters SCC” table within the 2002 NEI Version 3 Stack Parameter Default 

database. This stack parameter default database provides averages of the physical stack parameters per 

SCC based on all data in the 2002 NEI Version 3. This SCC match was successful for all but one data 

record (a record at the SCAQMD Facility ID 800016). For this one data record that was not assigned 

estimated physical stack parameters based on NEI facility data or on NEI SCC data, the record’s source 

industrial classification (SIC) was cross-referenced to the “Stack Parameters SIC” table within the stack 

parameter default database. Appendix B shows the physical stack parameters assigned to each SCC 

associated with Pb emissions at each of the 144 Pb-emitting point source facilities within 25 km of the 

airport. 

In addition to Pb emissions, SCAQMD also provided operating schedules for the Pb-emitting point source 

facilities. The following operating schedule data were provided for each source location: 

 Number of operating hours per day; 

 Number of operating days per week; and 

 Number of operating weeks per year. 

All of the facilities were in operation at least 5 days per week and at least 48 weeks per year in 2006, but 

without more detailed information about which weeks a facility was non-operational, it was assumed that 

every facility was in operation for every week of the year. Also, all facilities operating 5 days per week 

were assumed to operate Monday through Friday. Since information was available on the number of 

operating hours per day, hourly emissions were developed for three day-of-week groups: weekday 

(Monday through Friday), Saturday, and Sunday. For example, if a facility was reported to operate 6 days 

of the week it was assumed to operate Monday through Saturday (see Appendix B for the hourly and 

daily operation schedules). For hourly operations, the SCAQMD inventory provided the number of hours 

per day that the facility operated. It was assumed that this hourly activity was centered on 1300 Local 

Time (LT), though we performed some rounding in order to obtain emission amounts for whole hours 

rather than half-hours. For example, if a facility operated 13 hours of the day, it was assumed to mean the 

facility operated 0630 LT to 1930 LT. However, in order for emissions data to occupy whole hours, it was 

first rounded up to the closing time of 2000 LT (i.e., operating through the 1900 LT hour). This rounding 

forced the opening time to be 0700 LT (2000 LT - 13 hours). Thus, a facility that operated 13 hours of the 

day would have emission estimates for the hours of 0700 LT through 1900 LT. 

Ninety facilities were reported to operate 24 hours a day, 7 days a week. Of the 54 facilities that did not 

operate every hour of every day of the week, 37 operated only during 5 days of the week and 11 operated 

during 6 days of the week. Independent of the number of operating days per week, 25 facilities operated 

19 The 22 SCAQMD matched facilities were matched to 20 facilities in the NEI: 13 of the NEI facilities had only 

one Pb-emitting stack; 2 had 2 stacks with different stack parameters; 2 had 3 stacks (for one, 2 stacks were the 

same; for the other, all 3 stacks were the same); 1 had 4 stacks (3 were the same); 1 had 9 stacks (all different); and 

1 had 27 stacks (26 were the same). 

 47 
only 8 hours of the day, 7 operated 10 hours, 5 operated 12 hours, 1 each operated 13 and 14 hours, 8 

operated 16 hours, and 3 operated 18 hours. 

4.1.5 Emissions Summary 

Table 4-15 summarizes the emission inventory in the vicinity of Santa Monica Airport. The inventory 

shows the emission rates as discussed in each subsection of this Chapter. It should be noted that the area 

source emission category, while a relatively large source category, is distributed over some 36 square 

kilometers, while the emissions from the piston-engine aircraft are mostly concentrated within the 0.81 

square kilometer of the Santa Monica Airport. 

The total emissions for the piston-engine aircraft total some 118.6 kg/yr. This compares with the approach 

that uses national default data, as described in Section II of EPA (2008), which estimated annual Pb 

emissions at Santa Monica in 2002 of 363 kg. The inventory developed here reflects an improved 

inventory because it makes use of site specific information including: 

 the fleet of aircraft operating at Santa Monica; 

 activity data from 2008 rather than 2002; 

 facility specific time-in-mode activity for piston-engine aircraft; and 

 the fraction of piston-engine aircraft that are single- versus twin-engine aircraft. 

Table 4-15. Summary of the Lead Emissions Inventory for All Sources in the Vicinity of Santa 

Monica Airport (2008) 

Source Lead Emissions (kg/yr) 

Area Sources1

 67.0 

Three Major Roadways 0.04 

Point Sources2

 27.5 

Piston-engine Aircraft Emissions by Mode 

Taxi To Runway 20.4 

Run-up 13.5 

Takeoff Roll 10.0 

Climb-out 37.9 

 Approach 17.9 

Landing 9.4 

Taxi to Apron 9.5 

Total: 213.1 

1 Total emissions from all 9 2x2 km grid squares.
 2 All point sources with 20-km radius.
 

4.2 MODEL SELECTION AND CONFIGURATION 

The U.S. EPA’s AERMOD (Version 07026) model was selected as the preferred model for the air quality 

analysis. AERMOD has undergone extensive model testing and evaluation in recent years and represents 

the current state-of-the-science. It is the most appropriate air quality model tool for assessing the Pb 

emission impacts from piston-engine aircraft using leaded avgas, as well as the other smaller but widely 

dispersed emission sources within the local community. The model includes treatment for an urban 

nighttime boundary layer; applicability for all terrain types; a state-of-the-science approach for 

characterizing the fundamental boundary layer parameters; a treatment for plume meander; and a state-ofthe-science wet and dry deposition model. Both the plume meander and the updated planetary boundary 

 48 
 

layer surface and mixed layer scaling formulations are critical to the modeling of the near-field 

concentration gradient. 

 AERMOD was run using the following options: 

 U.S. EPA regulatory default options; 

 URBANOPT with default urban surface roughness; 

 No treatment for building downwash effects; 

 Direction-specific dispersion processing (land use based using AERSURFACE); 

 Complex/intermediate terrain algorithms; and 

 Wet and dry deposition. 

The URBANOPT option was coupled with the URBANSRC keyword for developing a nighttime urban 

boundary layer. The urban boundary layer height was determined based on population, per discussion 

with the South Coast Air Quality Management District (Tom Chico), using a Los Angeles County 

population of 10,000,000. 

Wet and dry deposition was included in modeling the air quality impacts. AERMOD has two methods for 

estimating dry deposition. Method 2 is used when the particle size mass distribution is not well known 

and only a small fraction of the total Pb mass is in particles with diameters larger than 10 microns. This is 

the case in this study so Method 2 was used in the analysis. Wet deposition makes use of hourly rainfall 

information using the algorithm implemented in AERMOD. 

Point sources were modeled using standard point source information on location, stack height, stack 

diameter, exit velocity, and temperature. All aircraft-related emission sources were modeled as volume 

sources. Roadways near the facility (Bundy/Centennial, Ocean Park and 23rd St.) were modeled as 

“areapolygon” sources. 

4.2.1 Runway Configuration and Aircraft Wake Turbulence 

Fixed-wing Aircraft 

To address the near-field spatial distribution of emitting sources and accommodate the characteristics of 

aviation source configurations, a grid spacing of 50 meters was used for the runway and takeoff and climb 

out for fixed-wing aircraft. This distance balances the computational requirements with sufficient source 

density to preserve the horizontal geometry of the source configuration and accurately simulate the nearfield concentration gradient. The approach used here is similar to the approach developed by Piazza 

(1999) but with some additional enhancements, particularly for the modeling of the run-up. 

Vertical (sigma z) and horizontal (sigma y) dispersion parameters were developed for moving (dynamic) 

sources following a mixing zone residence time approach. Sigma y parameters were developed by 

dividing the source separation distance by a standard deviation of 2.15; this is the standard methodology 

used in AERMOD. For initial sigma z, we used the mixing zone residence as defined in CALINE3 model 

by the following equation: 

 W 2  60 

0.2 

SZI  1.8  0.11 

   

  

  U   30 

Where: 

SZI = initial vertical dispersion (m) 

 49 
 

 

 

W2 = half width of the runway or taxiway (m) 

U = average wind speed (m/s) over the modeling period 

θ = angle between the runway and wind direction 

This equation accounts for the longer time an air parcel spends in the turbulent mixing zone and hence the 

greater initial vertical dispersion. Initial sigma y and initial sigma z were developed for each mode of 

aircraft operation as described below: 

Taxi 

Initial sigma z 

Width of taxiway = 80 feet (24.4 m) or W2 = 12.2 m; then apply equation above to estimate 

initial sigma z using the period average wind speed, U. 

Initial sigma y 

The horizontal separation distance between source centers is 50 m, thus the initial sigma-y = 

50/2.15 or 23.8 m. 

Takeoff/Approach/Landing/Climb-out (all treated the same) 

Initial sigma z 

Width = 35 feet20 (average aircraft wingspan) or W2 = 5.34 m, using the equation above using the 

period average wind speed, U. 

Initial sigma y 

The horizontal separation distance between source centers is 50 m, thus the initial sigma-y = 

50/2.15 or 23.8 m. 

For the in-flight segment for fixed-wing aircraft, an additional consideration was made to account 

for the wake turbulence created by the forces that lift the aircraft. High pressure air from the 

lower surface of the wings flows around the wing tips to the lower pressure region above the 

wings. A pair of counter-rotating vortices is shed from the wings where the right and left wing 

vortices rotate. It is within this region of rotating air behind the aircraft where wake turbulence 

occurs. To account for this effect, the effective emission height was adjusted for the angle of 

climb (takeoff) and glide slope angle for landing. This adjustment lowers the effective emission 

height to approximate the maximum downward extent of the aircraft’s trailing wake. For SMO, 

this resulted in an angle of climb out for takeoff of approximately 4.8 degrees, while for landing 

this was 2.8 degrees. 

20 Based on Montgomery and Foster (2006). 

 50 
 

 

 

 

 

 

 

Run-up 

Initial sigma z 

Initial sigma z (total) is a total combination of: 

Height above ground  Exhaust buoyancy  Wind flow over stationary aircraft 

Where: 

Height above ground = 1.0 m (typical tailpipe height on piston-engine aircraft) 

Exhaust buoyancy = 0.65 m21 

Wind flow over stationary aircraft = Typically two aircraft undergo run-up testing in staging 

area (total area with safe separation distance 100 feet) 

thus W = 30.48 m or W2 = 15.24 m. Then the initial 

sigma z equation (SZI = (1.8 + 0.11* (W2 / U)) * 

(60/30)0.2) is used to determine contribution from wind 

flow over aircraft. 

Then sum these three terms using the period average wind speed, U, to estimate the initial sigma 

z 

Initial sigma z 

Initial sigma-y is a total combination of: 

Wingspan wake  Horizontal momentum  propeller turbulence wake 

Where: 

Wingspan wake = Typically has two wing spans over run-up area (100 feet) or 

W=30.48 m, thus the initial sigma-y from wingspan wake = 

30.48/2.15 or 14.18 m 

Horizontal momentum = 0.6 m22
 

Propeller turbulence wake = 0.85 m23
 

Total initial sigma-y during run-up = (14.18+0.60+ 0.85) m = 15.63 m 

Rotorcraft (Helicopters) 

For rotorcraft, initial sigma z during idle was based on the typical piston-engine helicopter source height 

of 2.0 m divided by 2.15, or 0.93 m. Initial sigma y was based on the typical helicopter rotor width of 10 

m divided by 4.13, or 2.33 m. For takeoff and climb-out, the flight pathway was based on what was used 

for the fixed-wing aircraft because Santa Monica’s noise mitigation program asks that helicopters operate 

in the same flight path as fixed-wing aircraft.24 For landing, the rotorcraft are asked to approach from the 

21 Based on sensitivity test with SCREEN3 with and without exhaust temp of 573K. 22 Based on a sensitivity test with SCREEN3 with and without typical exhaust flow of 100 ft3

 per minute 23 Based on a typical 6-foot propeller size or 1.83 m; thus initial sigma-y equals 1.83 m/2.15 or 0.85 m 

24 City of Santa Monica – Requested Flight Paths (d) Helicopter, available at 

http://www01.smgov.net/airport/n_flights.aspx 

 51 
 

north or south, perpendicular to the runway, and then descend in a circular motion through 270 degrees 

onto the taxiway with a descent rate of 3 m/s starting at about 275 m (900 feet). The wake turbulence also 

occurs for rotorcraft as high pressure air on the lower surface of the rotor blades flows around the tips to 

the lower pressure region above the blades. Consequently, air is forced in a downward trend below the 

main rotor. This combination of actions results in an angle of descent for rotorcraft of 3.7 degrees. 

4.2.2 Terrain and Land Use 

The preprocessor tool AERMAP was used to characterize the terrain height and hill height scale. This 

analysis used data from the Digital Elevation Model (DEM) dataset with 7.5-minute arrays and 30-m 

horizontal resolution. These data were also used to determine the heights for each of the receptor 

locations. 

The preprocessor tool AERSURFACE was used to characterize the land use for the site and season 

specific albedo, Bowen ratio25, and surface roughness length. AERSURFACE uses as input the land cover 

data from the U.S. Geological Survey (USGS) National Land Cover Data 1992 archives (NLCD92). 

Given that the area has been urbanized for well over 30 years, the 1992 land use was considered 

representative of the area today. The recommended surface roughness radius of 1-kilometer (centered on 

the meteorological tower) was used in determining the local surface roughness. Examination of the land 

use using GIS showed no obvious way to create sectors, thus generic 30-degree sectors were developed as 

shown in Table 4-16. Figure 4-8 illustrates the land use pattern in the vicinity of the ASOS 

meteorological tower. By far the three most predominant land uses within 1-km of SMO are low intensity 

residential, commercial/industrial/transportation, and high intensity residential, which combined comprise 

86% of all land use types. By default, both the albedo and Bowen ratio were evaluated out to 10 km 

without a sector approach using AERSURFACE. 

Table 4-16. Surface Land Use Types (%) within 1 Kilometer Radius of SMO 

Sector 1 2 3 4 5 6 7 8 9 10 11 12 

Starting Direction 0 30 60 90 120 150 180 210 240 270 300 330 Total 

Low Intensity 

Residential 30.9 16.1 38.1 44.8 61.9 58.1 47.1 29.9 41.0 34.5 38.1 41.1 40.1 

High Intensity 

Residential 17.5 6.2 1.7 5.5 4.1 6.2 2.7 3.5 14.8 23.2 28.2 19.5 11.1 

Commercial/ 

Industrial/ 

Transportation 

33.7 50.7 46.7 41.0 26.5 28.5 43.3 45.5 28.6 20.8 24.7 25.3 34.6 

Bare Rock/Sand/ 

Clay 8.6 18.8 0.7 0.0 0.0 0.0 0.7 9.0 2.4 3.1 2.1 3.1 4.0 

Deciduous Forest 0.0 0.0 0.3 0.0 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 

Evergreen Forest 0.3 0.7 0.0 0.0 0.3 0.3 0.3 0.7 0.0 1.4 0.0 0.3 0.4 

Mixed Forest 0.3 0.7 0.7 0.0 1.4 1.0 0.3 5.6 2.8 0.7 1.4 3.8 1.5 

Shrubland 7.6 6.2 8.3 3.1 4.5 3.4 3.1 3.8 5.9 5.5 4.8 6.2 5.2 

Grasslands/ 

Herbaceous 0.3 0.3 3.5 4.8 1.0 2.1 2.4 1.4 1.7 1.4 0.7 0.3 1.7 

Pasture/Hay 0.0 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.1 

Urban/Recreational 0.7 0.0 0.0 0.7 0.0 0.3 0.0 0.7 2.8 9.6 0.0 0.0 1.2 

25 Bowen ratio: ratio of sensible heating to latent heating. 

 52 
Source: NLCD (1992). 

Figure 4-8. Land use in the Vicinity of the Santa Monica Airport. 

Seasonal adjustments for input to AERSURFACE were made to reflect the two predominant seasons of 

the Mediterranean climate of Santa Monica: a rainy mild season from November through April and a very 

dry mild season from April through November. The albedo varied from 0.16 to 0.17 and the Bowen ratio 

from 1.91 (September through February) to 1.70 (March through August). 

4.2.3 Meteorological Data 

Santa Monica Airport began collecting meteorological data in March of 2007 using a Handar/Vaisala 2-D 

sonic anemometer for wind speed and direction. The meteorological tower is located near the north end of 

the runway. This sonic anemometer is able to measure low wind speeds (< 1 m/s) and an archive of the 

rolling 2-minute wind data (recorded every minute) is archived by the National Climatic Data Center 

 53 
(NCDC). This wind monitoring system is operated as part of NOAA’s Automated Surface Observation 

System (ASOS). The 2-minute average wind data were downloaded from the National Climatic Data 

Center website at: ftp://ftp.ncdc.noaa.gov/pub/data/asos-onemin/ for both the winter and summer 

monitoring periods, as well as the 2008 one-year modeling period. The wind data were then provided to 

EPA to process (using a utility that is being developed for eventual public release) 2-minute average wind 

speed and direction data into hourly averages for use in AERMET. This processing involves a number of 

steps dealing with issues such as missing data and data truncation. For periods in which the 2-minute 

wind data were missing, the routine hourly ASOS data as archived on the NCDC website was used in the 

analysis. In addition, these hourly data include the hourly temperature and cloud cover data for use in 

AERMET. 

The nearest upper air station is the SCAQMD’s RASS profiler located at LAX, which measures hourly 

virtual temperature profiles starting at about 150 to 200 meters above ground level with additional 

temperatures reported at about 60 meter intervals up to approximately 700 to 1500 meters, depending on 

atmospheric conditions. However, the profiler was down during both the summer and winter monitoring 

period and was also frequently intermittent during 2008. In its place we used the SCAQMDrecommended upper-air data from the Miramar Naval Air Station (KNKX), which is the station routinely 

used by SCAQMD in their air quality assessments. 

In all cases, the meteorological data were processed through the AERMET (version 06341) using the 

upper-air data to determine the convective mixing height (an estimate of the potential daytime mixing 

height). The convective mixing height is determined from the surface temperature and the vertical 

variation in the potential temperature as observed from the morning sounding. The daytime mixing height 

is determined as the highest between the convective and mechanical mixing height. In addition, AERMET 

calculates the local sensible heat flux, convective velocity scale, vertical potential temperature gradient, 

and Monin-Obukhov length, all of which are used as input to AERMOD. 

4.2.4 Background Ambient Conditions 

Pristine background air quality concentrations have been summarized by EPA’s Office of Air Quality 

Planning and Standards (OAQPS) in the Regulatory Impact Analysis (RIA) for the proposed revision of 

the Lead NAAQS (USEPA, 2008). The pristine background ambient Pb concentration in the RIA is 0.5 

ng/m3

. Additional emissions from regional point sources and other area wide sources, as discussed earlier, 

increase pristine background levels to levels termed either ‘regional’ or ‘urban’ background levels. The 

regional background concentrations, as measured during MATES-III, ranged from 5 to 10 ng/m3

, as 

reported by SCAQMD for the basin-wide ambient air measurements of Pb concentrations made during 

the MATES-III monitoring program (April 2004 through March 2006). The monitored SCAQMD values 

are shown in Figure 4-9 below. The nearest monitoring site to SMO is Burbank. 

4.2.5 Receptors 

To fully define the spatial extent of elevated Pb concentrations within the vicinity of the airport, receptors 

were placed in a nested Cartesian grid with receptor spacing as follows: 

 50-meter grid spacing extending 1 km around the facility boundary; and 

 100-meter grid spacing extending out to 2 km around the facility boundary. 

Receptors were also placed at 50 meter intervals around the airport boundary fence line. In addition, 

receptors were placed on the airport property to evaluate Pb concentrations where members of the general 

public may visit, such as the airport hangars, access roadways, and observation locations. The only area 

excluded was the active runway. A total of 178 on-airport receptors were identified. Figure 4-10 shows 

the location of the on-airport property receptors. 

 54 
Source: MATES-III South Coast Air Basin, Final Report, September, 2008. 

Figure 4-9. Ambient lead monitoring in the South Coast Air Basin (April 2004 – March 

2006). 

Figure 4-10. On-airport air quality modeling receptors. 

 55 
Sensitive Receptors 

Site-specific sensitive receptor locations were included within 2 kilometers of the airport. Sensitive 

receptors are specific locations where Pb concentrations are needed for the study. For this analysis we 

identified sensitive receptors for day care centers, senior centers, hospitals, schools, recreational areas, 

and playgrounds. Sensitive receptors were identified through a combination of ESRI ArcGIS v9.3 

“shapefiles” and GoogleEarth. A total of 62 sensitive receptors were identified, including 28 schools, 21 

churches, 2 hospitals/health centers, 7 parks/playgrounds/golf courses, 1 senior center, and 3 recreation 

centers. Figure 4-11 shows the locations of the nearby neighborhood and sensitive receptors. 

Figure 4-11. Air quality modeling receptors in the vicinity of SMO. 

 56 
 

4.2.6 Selected Modeling Scenarios 

This section first discusses the basis for the selection of the days for air quality modeling for the model to 

monitor comparison. For this model-to-monitor comparison, three days each were selected from the 

winter and summer air monitoring campaigns. Also discussed is the basis used for selecting the maximum 

3-month average from the year long modeling of 2008, which was then used in the sensitivity analysis. 

Winter Modeling Days 

Ideal days for the model-to-monitor comparison are characterized as having a full set of Pb monitoring 

data for both the upwind and downwind monitoring sites as well as day-specific hourly meteorological 

data and information on the hourly aircraft activity data, particularly the number and type of piston-engine 

aircraft and duration of engine run-up times (these are important source contributors for the east tarmac 

and residential monitoring locations). The time-in-mode survey data on taxi, engine run-up, climb out, 

approach, landing and takeoff times were collected on March 13, 14, 15 and then again on March 27, 28 

and 29. Subsequent review of the survey data showed that engine run-up time duration was improperly 

collected on three of these days and not representative of the actual period in which the aircraft engine 

operated at high RPM. Thus, the three remaining days (March 14th, 28th and 29th) were selected for the 

winter model-to-monitor comparison. 

Summer Modeling Days 

Likewise, three days from the summer monitoring program were selected for model-to-monitor 

comparison. Monitoring was conducted from July 25th through July 31st. Unlike the winter program, no 

hour-specific aircraft activity data were collected. Thus, the availability of valid data and high 

concentrations were the determining factors for selecting the three preferred modeling days. The daily 

total number of piston-engine aircraft operations was provided by Santa Monica Airport staff. The two 

days with the highest monitored concentrations were July 26th and July 28th, which had similar high 

concentrations of 58 and 62 ng/m3

 at the East Tarmac site but had very different numbers of daily total 

piston-engine aircraft operations, 103 and 377, respectively. The meteorology appeared similar between 

these two days. These two days were selected for modeling to evaluate how well the model could 

simulate these differences in aircraft operations. The third highest day (without background) was July 

27th and it was selected as the third day for the model-to-monitor comparison. 

Modeling 2008 and the Maximum 3-month Average 

All emission sources were modeled with AERMOD for each day of 2008. This was done to determine the 

local gradient in Pb concentrations and to identify the sources contributing to elevated ambient Pb in the 

vicinity of the airport. In addition, the modeling results for 2008 were analyzed to determine the 

maximum 3-month rolling average Pb concentrations at all receptors to provide data that could be 

compared with the National Ambient Air Quality Standard for Lead of 150 ng/m3

. The maximum 3­

month average period was also the focus of the sensitivity analysis. All emission sources were modeled 

with AERMOD for all of 2008 and the the results were analyzed to determine the highest 3-month rolling 

average Pb concentrations. The analysis showed that the highest Pb concentrations occurred at most 

receptors during the summer months (June to August). Thus, the three summer months of June through 

August were selected as the maximum 3-month period for the sensitivity analysis. 

A review of the general aviation activity data at Santa Monica Airport showed that month-to-month 

variation in general aviation and air taxi activity was small (less than 15% variation) in 2008 (Figure 4­

12). Thus, the meteorology was the cause of the higher Pb concentrations modeled during the summer 

months (June to August). The meteorological factors influencing ambient Pb concentrations in the 

vicinity of the airport are discussed in Section 4.3.5. 

 57 
 

 

0 

50 

100 

150 

200 

250 

300 

350

Average Daily Operations of GA 

and AT Activity 

1 2 3 4 5 6 7 

Month 

8 9 10 11 12 

Figure 4-12. 3-month daily average general aviation (GA) and air taxi (AT) activity 

at Santa Monica Airport. 

4.3 MODELING RESULTS 

4.3.1 Winter Model-to-monitor Comparison 

Modeling results for the downwind receptors for the three March days are summarized in Table 4-17. For 

two of the three days (March 14th and March 29th), the modeled values paired in both time and space 

compare favorably to the measurements, with the mean absolute model-to-monitor difference less than 

30%. On March 28th, AERMOD over predicts, but the differences appear to be driven primarily by a few 

high hours in the early evening hours. For all three days modeled, the bias was -16.9 ng/m3

, the absolute 

bias was 19.5 ng/m3 and the absolute fractional bias was 0.29, well within a factor of two (0.67). The 

standard deviation was 17.4 ng/m3 and the root mean square error was 5.8 ng/m3

. 

Table 4-17. Model-to-Monitor Comparison for Winter 2009 at 

Santa Monica Airport Using ASOS SMO (1-min wind data) 

Station March 14th March 28th March 29th 

Modeled (ng/m3) 

Clarkson 56.5 86.0 75.4 

East Tarmac 46.1 61.8 94.1 

Observed (ng/m3

) 

Clarkson 41.7 N/A 44.9 

East Tarmac 52.6 39.3 70.6 

The time series results presented in Appendix C (Figures C-1 through C-6) show stacked plots of the 

modeled source contribution by emission source type: taxi, run-up, takeoff, climb-out, approach, and 

landing, with differentiation between southern (S) and northern (N) approach for taxi and landing as well 

as stratification by aircraft type – helicopter (H), multi-engine fixed wing aircraft (M) and single-engine 

fixed wing aircraft (S). The stack height for each source shows the relative contribution for that source 

type. In all cases, the single-engine run-up is the most important source contributor followed by the south 

taxi emissions from single-engines and then single-engine takeoff. This analysis of source contribution in 

 58 
 

 

 

the vicinity of the expected highest concentration reaches a markedly different conclusion about the most 

important emission source than an analysis that only examines total airport Pb emissions, which would 

show that approach and climb-out emissions are the most important emission sources. Finally, the timeseries figures all show a strong increase in concentration during the late afternoon/early evening hours 

when a ground-based inversion acts to limit the vertical mixing leading to high ground-level 

concentrations. To some extent this is likely real, but the increase in ground-level concentrations is likely 

overstated by the model. Hourly Pb concentrations would be needed to evaluate this phenomenon. 

Isopleth figures for each day modeled are presented in Appendix C (Figures C-7 through C-9). These 

figures show the elevated spatial Pb concentration gradient as well as monitored values. On the 14th, 

elevated concentrations above the Los Angeles basin-wide background concentration of 10 ng/m3 extend 

to the northeast to about Stoner Ave., about 500 meters from the airport fence line, and then northnorthwest to south-southeast from Ivy to Malone about 400 meters. Elevated Pb concentrations are also 

predicted in the observation deck area of about 15 ng/m3

. Spatial gradients on the 29th show elevated 

concentrations above the basin-wide background level extending to about 900 meters downwind and the 

concentrations in the observation deck area are predicted to be about the same as on the 14th. The 28th 

shows a similar pattern. 

4.3.2 Summer Model-to-monitor Comparison 

Modeling results for the three July days are summarized in Table 4-18. For two of the three days (July 

26th and July 28th), the model-to-monitor comparison shows excellent model performance, with the mean 

absolute model-to-monitor difference less than 10%. For July 27th, AERMOD over predicts; however, the 

AERMOD results on this day are strongly influenced by a few high hourly concentrations during 

midday.26 For all three days modeled, the bias was 5.7 ng/m3

, the absolute bias 4.4 ng/m3

 and the absolute 

fractional bias was 0.13, well within a factor of two (0.67). The standard deviation was 13.3 ng/m3 and the 

root mean square error was 8.8 ng/m3

. 

Table 4-18. Model-to-Monitor Comparison for Summer 2009 

at Santa Monica Airport Using ASOS from SMO (1-min wind 

data) 

Station July 26th July 27th July 28th 

Modeled (ng/m3) 

East Tarmac 54.6 33.0 56.7 

Resident 1 49.4 30.0 51.7 

Resident 2 38.3 19.6 35.7 

 Observed (ng/m3

) 

East Tarmac 57.7 53.1 62.2 

Resident 1 56.11

 37.91 53.81 

Resident 2 33.11 24.91 33.62 

1	 Data are adjusted from operating hours of the airport to 24-hour 

averages assuming a South Coast Basin background concentration of 

10 ng/m3

 during hours in which the airport is closed. 

2 Estimated 24-hour concentration as it was unknown when the air 

monitor stopped operating. 

26 Unlike the winter program, hourly activity information was unavailable for the summer program. The average 

piston-engine aircraft activity levels from the winter study were used in assigning the hourly activity levels. 

 59 
The time-series results presented in Appendix D (Figures D-1 through D-9) show stacked plots of the 

modeled source contribution by emission source type: taxi, run-up, takeoff, climb-out, approach, and 

landing with differentiation between southern (S) and northern (N) approach for taxi and landing as well 

as stratification by aircraft type – helicopter (H), multi-engine fixed wing aircraft (M) and single-engine 

fixed wing aircraft (S). The stack height for each source shows the relative contribution for that source 

type. In all cases, the single-engine run-up is the most important source contributor, followed by the south 

taxi emissions from single-engines and then the single-engine landing or multi-engine run-up. The highest 

concentration from point sources (almost 13 ng/m3

) occurs on July 27th, hour 6-7, at the East Tarmac. 

Similar to the winter sampling period, the time-series figures all show a strong increase in concentration 

during the late afternoon/early evening hours when a ground-based inversion acts to limit the vertical 

mixing, leading to high ground-level concentrations. To some extent this is likely real, but the increase in 

ground-level concentrations is most likely overstated by the model. Hourly Pb concentrations would be 

needed to evaluate this phenomenon. 

Isopleth figures for each day modeled are presented in Appendix D (Figures D-10 through D-12). These 

figures show the elevated spatial Pb concentration gradient as well as the monitored values. On the 26th, 

elevated concentrations above the Los Angeles basin-wide background concentration of 10 ng/m3 extend 

to the northeast to about Stoner Avenue, about 500-meters from the airport fence line, and then northnorthwest to south-southeast from Ivy to Malone about 400 meters. Spatial gradients are predicted to be 

similar for the 28th. On the 27th, however, elevated concentrations above the basin-wide background level 

extend only to Berkshire, about 400 meters downwind, and the concentrations at the observation deck 

area are predicted to be less than 10 ng/m3

. 

4.3.3 Summary of the Model-to-monitor Comparison 

Overall, the model-to-monitor performance was considered good to excellent as the results show good 

agreement with observations, particularly on 4 of the 6 days modeled. Modeling results have been paired 

in both time and space and have shown good overall agreement, well within the factor of two frequently 

sited as a goal in model-to-monitored air quality evaluations. Modeling results consistently show that runup emissions are a significant contributor to the highest concentrations at all of the downwind monitoring 

locations. In addition, both the summer and winter modeling studies made use of a detailed emission 

inventory for aircraft and other sources of Pb within 25 kilometers of Santa Monica Airport. This detailed 

emission inventory, along with the use of on-site ASOS data, were critical elements leading to the good to 

excellent model-to-monitor comparison. 

Further model-to-monitor comparisons could potentially be performed using the other days for which 

ambient monitoring data were collected, as well as using the additional 24-hour Pb concentration data 

collected by South Coast AQMD between April 2006 and March 2007 and the airport activity data 

available from FAA’s Air Traffic Activity Data System. A particularly interesting day to model would be 

November 19, 2006, which is when South Coast reported an observed daily average concentration of 299 

ng/m3

 at the East Tarmac monitoring location. 

4.3.4 Full Year Modeling Results 

Air quality modeling was performed using AERMOD for the 2008 calendar year. Year-long modeling 

results are provided in Appendix E. These data were evaluated to describe the spatial gradient in Pb 

concentrations, the seasonal variability in Pb concentrations and the relative influence of roadway Pb on 

ambient Pb concentrations. As shown in Appendix E the rolling 3-month average results show a similar 

spatial pattern in air Pb concentrations over the entire year, but with higher concentrations extending 

further downwind of the prevailing wind direction during the summer months. Concentrations above the 

South Coast urban background of 10 ng/m3 are modeled out to a distance of about 450 meters beyond the 

 60 
 

East Tarmac during June-August, but only extend out to about 300 meters from the East Tarmac during 

the December-February period. The lateral extent of concentrations above South Coast background is 

about 300 meters along Bundy Drive during the summer and winter periods and gradually shrinks with 

downwind distance. 

Roadway Contribution 

The year-long modeling results were also used to assess the relative importance of Pb exhaust emissions 

from on-roadway sources27. For this analysis, modeled air Pb concentration data were examined by 

looking at upwind/downwind differences across 23rd Street over the one-year modeling period. A pair of 

upwind/downwind receptors, as shown in Figure 4-13, were chosen such that the airflow between the 

receptors crossed the roadway. The wind directions that satisfy these conditions are between 190 and 230 

degrees. For 2008, a total of 1,984 hours fell within these wind directions. For all but one hour, the 

upwind concentration had zero concentration. Table 4-19 shows the average concentration differences in 

each 10-degree wind direction bin between 190 and 240 degrees. The maximum increase across the 

receptors (0.15 ng/m3

) occurred on December 10th with a wind direction of 194 degrees. The average 

increase for the 190-200 degree wind direction bin, however, was substantially less (0.029 ng/m3

). In 

Table 4-13 it is identified that the total entrained Pb road dust of 41.2 kg/yr is about 7.5 times higher than 

the total exhaust Pb emissions for the region (5.5 kg/yr). Thus the entrained Pb road dust average 

concentration should be no higher than 0.23 ng/m3

. The combined impacts from on-roadway mobile 

source Pb exhaust and entrained emissions are expected to be less than the average pristine ambient 

background concentration of 0.5 ng/m3

 and are therefore not expected to be a significant contributor to 

ambient Pb concentration levels. However, for 24-hour periods the Pb concentration from both exhaust 

and entrained road dust could reach as high as 1.3 ng/m3

. 

4.3.5 Maximum 3-month Average Modeled Concentrations 

The results from the full year 2008 modeling were compiled into 3-month rolling averages (e.g., JanuaryMarch, February-April, March-May, etc.) to facilitate selection of the maximum 3-month average 

concentration period and to identify the meteorological conditions which influence the highest 

concentrations of Pb. As shown in Figure 4-12, general aviation activity patterns are not particularly 

seasonally dependent at SMO (levels decrease less than 15% during the winter months). This analysis was 

designed to investigate whether there are large seasonal variations in air Pb concentrations and, if so, what 

meteorological conditions are the most important drivers. 

The 3-month rolling average concentrations for the 12 receptors with the highest concentrations are 

shown in Figure 4-14 (See Appendix F for the relative locations of these receptors). This figure shows a 

strong seasonal pattern for most of these high concentration locations, with most receptors showing a 

peak during the June-August period. The two receptors with 3-month average concentrations above 150 

ng/m3

 are located on airport property. Since the general aviation emission activity did not exhibit a similar 

pattern of seasonal change, the underlying cause was attributed to changes in meteorology. To investigate 

which meteorological variables were most important to the changes in 3-month average Pb 

concentrations, 3-month rolling averages were developed for the meteorological variables most likely to 

affect the concentration at a near source location. The set of meteorological variables examined were the 

3-month average of: wind speed, convective and mechanical mixing height, the atmospheric stability (in 

terms of anemometer height and the Monin-Obukov Length [z/L]), and the persistence of wind direction. 

These averages were determined using only those hours in which the airport was operating. 

27 Entrained road dust was not included as this information was only available at the 2 km x 2 km emission 

inventory resolution 

 61 
Figure 4-13. Upwind/downwind receptors along 23rd St. near Santa 

Monica Airport. 

Table 4-19. Average Increase in Ambient Pb 

Concentration along 23rd St. from On-road Mobile 

Source Exhaust Emissions 

Wind Direction 

Average increase in concentration 

(ng/m3

) 

190-200 0.029 

200-210 0.028 

210-220 0.020 

220-230 0.018 

230-240 0.016 

 62 
0 

50 

100 150 200 250 

Jan-Mar Feb-Apr Mar-May Apr-Jun May-Jul Jun-Aug Jul-Sep Aug-Oct Sep-Nov Oct-Dec Nov-Jan Dec

3 Month Period 

3 month Average Pb Concentration (ng/m3) 

Figure 4-14. 3-month rolling average concentrations for the 12 highest receptor locations for 2008 at Santa Mo
 

Figure 4-15 shows the seasonal wind speed pattern. Average wind speeds are about 1 m/s higher for the 

highest 3-month average Pb concentration period compared with the lowest 3-month average Pb 

concentration period. This pattern is not coincident with the Pb concentration pattern and does not appear 

to explain the maximum 3-month average concentration seen during the summer months. Similarly, the 

convective (Figure 4-16) and mechanical mixing heights (Figure 4-17) show lowest mean heights in the 

3-month period beginning in October or November and do not correspond with the concentration profile 

(i.e., lower mixing heights are typically related to higher ambient concentrations of pollutants emitted at 

ground-level). This finding is not entirely unexpected because aircraft run-up and taxi emissions dominate 

peak concentrations and should not be affected by the mixing height given the close proximity. 

Wind Speed 

0 

0.5 

1 

1.5 

2 

2.5 

3 

3.5 

JanMar FebApr MarMay AprJun MayJul JunAug JulSep AugOct 

m/s 

SepNov OctDec NovJan DecFeb 

Figure 4-15. 3-month rolling average wind speed at SMO. 

Convective mixing height 

0 

100 

200 

300 

400 

500 

600 

700 

800 

JanMar FebApr MarMay AprJun MayJul JunAug JulSep AugOct 

m

SepNov OctDec NovJan DecFeb 

 Figure 4-16. 3-month rolling average convective mixing height at SMO. 

 64 
 

Mechanical Mixing Height 

0 

100 

200 

300 

400 

500 

600 

m 

Jan- Feb- Mar- Apr- May- Jun- Jul- Aug- Sep- Oct- Nov- DecMar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb 

Figure 4-17. 3-month rolling average mechanical mixing height at SMO. 

Table 4-20 shows the number of hours of stable, neutral, and unstable conditions over the 3-month period. 

The number of hours with stable conditions reaches a minimum during the summer, which suggests that 

Pb concentrations should reach a minimum during the summer months due to more hours with better 

turbulent mixing conditions. However, this is the opposite of what is observed in the Pb concentrations. 

Table 4-20. Number of Hours over 3-month Period with 

Unstable, Neutral, and Stable Conditions at SMO 

Period 

Number of 

Hours Unstable 

(z/L < -1) 

Number of 

Hours Neutral 

(-1 < z/L < 1) 

Number of 

Hours Stable 

(z/L > 1) 

Jan-Mar 87 1,000 278 

Feb-Apr 89 983 278 

Mar-May 63 1,059 258 

Apr-Jun 43 1,101 221 

May-Jul 19 1,194 167 

Jun-Aug 29 1,203 148 

Jul-Sep 37 1,185 158 

Aug-Oct 77 1,054 249 

Sep-Nov 89 956 320 

Oct-Dec 104 895 381 

Nov-Jan 86 950 344 

Dec-Feb 90 963 312 

An examination of the persistency of wind direction was performed by binning the wind direction into ten 

degree bins during the hours in which the airport was open. The bins were grouped into six 10-degree 

bins (see Figure 4-18), spanning wind directions from 195-255 degrees. The runway is oriented at 223 

degrees.28 Examination of the downwind concentration pattern (Appendix E) shows that the highest 

28 Although the runway is labeled as 210, this is the magnetic compass reading rather than the true angle relative to 

north. SMO has a magnetic declination of 15 degrees east. 

 65 
concentration has an orientation axis of about 230 degrees. Figure 4-18 shows that the highest frequencies 

of this wind direction occur during July, with the second and third highest in August and June, 

respectively. Figure 4-18 shows that from June through August, over 50 percent of all hours had a wind 

direction between 225 and 245 degrees when the airport was open. This wind direction frequency pattern 

closely follows the pattern shown for the highest Pb concentrations. Thus, it appears that the persistency 

of wind direction plays an important role in determining the highest Pb concentrations. 

0.0% 

5.0% 

10.0% 

15.0% 

20.0% 

25.0% 

30.0% 

35.0% 

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

Month 

Frequency

 of Wind Direction 

195-205 205-215 215-225 225-235 235-245 245-255 

Figure 4-18. Frequency of wind direction at SMO. 

4.3.6 Sensitivity Analysis 

A set of seven sensitivity tests, plus the baseline, were conducted using the meteorological conditions for 

the maximum 3-month Pb concentration period (June-Aug). The seven tests that were chosen for those 

parameters were: (1) expected to represent the possible ranges that might be found at similar airport 

locations, and (2) expected to result in the largest changes in peak Pb concentrations. The concentrations 

for the top 12 receptors are shown graphically for each sensitivity test in Figure 4-19. All 12 receptors are 

located in close proximity to runway 21, both on-airport and off-airport. Figure 4-20 shows the locations 

of the top 12 receptors for the baseline case. 

A set of sensitivity tests were selected with the intent to characterize the impact of these parameters on 

ambient Pb concentrations. The key parameters used in the sensitivity analysis are identified in Table 4­

21. The set of sensitivity analyses were applied to the maximum 3-month average and included receptors 

both within the airport property where the public might have access, at the fence line, and downwind of 

the airport. The specific sensitivity tests and their associated baseline, low-end, and high-end values are 

provided in Table 4-21. 

 66 
 

12 Top Receptors Among the 8 Sensitivity Tests, and Their 

Concentrations Among Those Tests. X-Axis Organized by Low270 

Concentration (ng/m3) 220 

170 

120 

70 

20 

High Tests. 

Baseline High Lead Low High Low Taxi High Taxi Low Twin High Twin 

Runup Runup Out Time Out Time Count Count 

Sensitivity Test 

366563 _ 3765404 366552 _ 3765423 366567 _ 3765378 366583 _ 3765395 

366587 _ 3765411 366576 _ 3765445 366536 _ 3765445 366587 _ 3765461 

366547 _ 3765456 366565 _ 3765354 366631 _ 3765449 366637 _ 3765461 

Figure 4-19. Sensitivity tests for the maximum 3-month average period (June-August). 

Figure 4-20. Locations of top 12 receptors found in sensitivity tests. 

 67 
 

 

 

 

Table 4-21. Ranges in Key Parameters for Pb Sensitivity Tests at Santa Monica Airport 

Parameter Low End Baseline High End 

Fraction of Fixed-wing Multi-engine 

Piston-engine Aircraft 

0 0.025 0.12 

Average “Run-up” time (seconds) 30 89 120 

Taxi-out Time (seconds) 160 304 549 

Lead Content in Avgas (g/gal) 2.12 2.12 2.59 

All of the baseline values come from the time-in-mode survey data described in section 4.1.1 except for 

the Pb content in avgas, which was based on the ASTM standard for 100LL. The range of the fraction of 

activity conducted by multi-engine aircraft was derived from the number of aircraft based at the airport, 

as reported to FAA in its Master data records available through www.airnav.com. For the period ending 

May 2009, 35 of the 303 aircraft (12%) based at SMO were multi-engine aircraft. The range in “run-up” 

time was based on interviews with two pilots and a flight instructor.29 The range in taxi-out time was 

based on the 5th and 95th percentiles observed during the time-in-mode survey. The Pb content in avgas 

reflects that at the Santa Monica Airport only 100LL avgas is available and the ASTM standard for 

100LL is 2.12 g/gal. The high end represents the highest Pb concentration measured from fuel samples 

collected at the Santa Monica Airport in March 2009. 

As shown in Figure 4-19, the increase in Pb fuel content over the baseline resulted in modest increases in 

air Pb concentration. The range of air Pb concentration increases was higher for the increase in the 

fraction of multi-engine aircraft. The largest changes in air Pb concentrations occurred over the span 

between the shortest engine run-up time of 30 seconds and the high end run-up time of 120 seconds. In all 

cases, except the low-end engine run-up, at least one receptor showed a concentration greater than 150 

ng/m3

. The highest number of receptors above 150 ng/m3 occurred for the high engine run-up scenario, 

with five receptors above 150 ng/m3

. Based on this analysis, the engine run-up time was determined to be 

one of the most important parameters in determining near-field Pb concentrations. The parameter which 

appeared least sensitive was the taxi-out time. 

Appendix F shows the air Pb concentrations by sensitivity test at each receptor by color-coded bins and 

by contours for the maximum 3-month concentration period. Each figure shows the spatial concentration 

gradient for each sensitivity test. The high run-up time shows that air Pb concentration levels remain 

above the South Coast Basin background (10 ng/m3

) out to a distance of 500 meters from the airport 

property line, whereas the low engine run-up only showed elevated concentrations out to 300 meters from 

the airport property line. 

4.3.7 AERMOD (07026) versus AERMOD (09292) 

Near the completion of this study, EPA released a new version of AERMOD (09292). To evaluate the 

potential implications of this new version of the model on this study’s findings, the new version of 

AERMOD (09292) was run for March 29, 2009, using only the emissions associated with the singleengine run-up. These results were then compared with the earlier results for the same scenario using 

AERMOD 07026 for any receptor where the simulated concentrations exceeded a minimum of 10 ng/m3

. 

29 Dr. Richard Pat Anderson, Director of the Flight Research Center at Embry-Riddle Aeronautical Universtiy in 

Daytona, FL reported that their experienced pilots conduct run-up checks for a total of 1 minute and their pilots in 

training for 2 minutes. Two private pilots reported lower estimates of about 30 seconds total. 

 68 
 

A total of 204 receptors had hourly concentrations that exceeded 10 ng/m3. These receptors had multiple 

hourly occurrences resulting in a total of 725 unique time and locations exceeding the 10 ng/m3

 threshold. 

In all cases, the percent difference between the two versions of AERMOD was less than 1%. Figure 4-21 

shows the percent difference at each unique receptor/time combination. The largest difference (0.72%) 

was along the fence line near the run-up location but it was not the highest concentration (only 126th 

highest out of the 725 pairings); otherwise, all of the differences were less than 0.5%. Similar results 

would be expected for other days and scenarios. As a result, it is not anticipated that the latest version of 

AERMOD will have any appreciable impact on any of the findings or conclusions from this study. 

0.80%
 

0.70%
 

0.60%
 

0.50%
 

0.40%
 

0.30%
 

0.20%
 

0.10%
 

0.00%
 

0 100 200 300 400 500 600 700 800 

Location and Time 

Figure 4-21. Ranked absolute value of percent difference of AERMOD (09292) 

and AERMOD (07026) for single-engine run-up emissions on March 29, 2009. Abs Percent Difference 

 69 
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 70 
 

5 Summary and Conclusions 

In this study, data inputs for AERMOD were developed and applied to evaluate local-scale concentrations 

of Pb in the ambient air in the vicinity of an airport servicing piston-engine aircraft operating on leaded 

avgas. Specific analyses included model evaluation by comparing modeled data to ambient air quality 

monitoring during two seasons in 2009, spatial and seasonal variability in modeled Pb concentrations for 

2008, and evaluation of the factors influential for the maximum 3-month average in 2008. 

The air quality monitoring was performed in two campaigns: a winter campaign over two weekend 

periods in March 2009 and a summer campaign over a one week period in July 2009. Monitoring data 

were collected on a 24-hour basis at up to 4 locations in the vicinity of the airport. Dust and soil Pb 

sampling was collected during the summer air monitoring campaign. 

The comprehensive emission inventory developed for this study included a detailed characterization of: 

stationary sources, area sources, on-road and non-road sources, and a detailed piston-engine aircraft 

emission inventory. The aircraft emissions data used in the model simulated the various aircraft operating 

modes, with the following modes considered: taxi-out, engine run-up, takeoff, climb-out, approach, 

landing, and taxi-in. A time-in-mode site survey was performed on aircraft operations during the winter 

campaign to collect information on the characteristics of the aircraft (specifically, the number of engines) 

and length of time piston-engine aircraft spend in each operating mode. 

Site-specific air quality modeling was performed using day-specific aircraft operations, on-site twominute rolling average wind speed and direction data, and site-specific terrain and land use information. 

Receptors were placed both within the airport property as well as in the surrounding community. 

A detailed model-to-monitor comparison was completed for both the winter and summer campaigns. In 

addition, a complete one-year period (2008) was modeled using daily aircraft activity and, using these 

results, the maximum 3-month average Pb concentration period was identified for subsequent sensitivity 

tests. The sensitivity tests evaluated Pb concentration responses to changes in avgas Pb content, duration 

of engine run-up, taxi duration times, and fraction of multi-engine aircraft activity. 

5.1 CONCLUSIONS 

The model-to-monitor comparison for the winter campaign showed good agreement between the modeled 

and observed results (paired in time and space), with an absolute mean bias of 19.5 ng/m3 and an absolute 

fractional bias of 0.29, well within a factor of two (0.67) of the observed and modeled concentrations. The 

most important source contributors to the highest air Pb concentrations were emissions associated with 

the single-engine aircraft run-up, followed by the taxi and takeoff emissions from single-engine aircraft. 

For the winter campaign, the model predicts elevated concentrations above the South Coast basin-wide 

background concentration of 10 ng/m3 extend downwind of the airport ranging from about 500 to 900 

meters from the airport fence line relative to a concentration of 56 to 86 ng/m3

 at the East Tarmac. 

The model-to-monitor comparison for the summer campaign showed even better agreement than those in 

the winter campaign, with an absolute mean bias of 4.4 ng/m3 and an absolute fractional bias of just 0.13, 

again well within the factor of two (0.67) of the observed and modeled concentrations. The summer 

modeling continued to show that single-engine run-up is the most important contributor to the peak air Pb 

concentrations. For the summer campaign, the model predicts elevated concentrations above the Los 

Angeles basin-wide background concentration of 10 ng/m3 extend downwind of the airport ranging from 

about 400 to 500 meters from the airport fence line relative to a concentration of 33 to 55 ng/m3

 at the 

East Tarmac. 

 71 
 

Both the summer and winter modeling studies made use of a detailed emission inventory for aircraft and 

other sources of Pb within 20 kilometers of Santa Monica Airport. This detailed emission inventory, 

along with the use of on-site ASOS data, were critical elements leading to the good to excellent model-tomonitor comparison. 

Year-long modeling showed that the maximum 3-month concentration was highly influenced by the 

persistency in wind direction during the period (June-August) and not by changes in aircraft activity. It 

was observed that during airport operating hours from June through August, over 50 percent of all hours 

had wind directions between 225 and 245 degrees. Modeling results showed that two receptors had the 

potential for having a 3-month average concentration above 150 ng/m3

; both receptors are located on the 

airport property in close proximity to the blast fence. Concentrations off airport property were modeled to 

have concentrations as high as 120 ng/m3

. 

A set of seven sensitivity tests were completed for the maximum 3-month average period. The tests were 

chosen for those parameters expected to represent the possible ranges that might be found at similar 

airport locations and that were expected to have the largest impacts on ambient Pb concentrations. The 

parameter which resulted in the largest changes over the ranges modeled was the engine run-up time, 

followed by the Pb concentration in the fuel, and then the fraction of multi-engine aircraft. Little change 

in concentration occurred with changes in taxi times. The run-up time showed the greatest impact on the 

spatial extent of the Pb concentration levels. The high run-up time showed that the Pb concentration could 

remain above South Coast Basin background (10 ng/m3

) out to a distance of 500 meters from the airport 

property line, whereas the low engine run-up only showed elevated concentrations out to a distance of 

about 300 meters from the airport property line. 

The year-long modeling results were also examined to determine the relative importance of Pb exhaust 

and entrained road dust emissions from on-roadway sources. Modeled receptors were examined looking 

at upwind/downwind differences across the relatively busy road, 23rd Street. The combined impacts from 

on-roadway mobile source Pb exhaust and entrained Pb emissions were shown to be less than the average 

pristine ambient background concentration of 0.5 ng/m3

 and are therefore not expected to be a significant 

contributor to ambient Pb concentration levels. 

5.2 IMPLICATIONS FOR OTHER AIRPORTS 

The approach used here would be fully applicable to other airports. However, complications not dealt 

with here that may occur at other airport locations include multiple runways and multiple prevailing wind 

directions. These additional complications can be handled within the framework used in this study, but 

would require additional effort to include runway layout geometry and changes in emission source 

locations depending upon wind direction. 

Based on the experience gained from this analysis, it is recommended that modeling for other airport 

locations focus available resources on efforts to assemble data for the following key areas: 

	 Conduct an on-site survey of the duration and location of LTO modes for piston-engine aircraft, 

with particular emphasis on the duration of run-up times and location(s) 

	 Collect information on hourly activity patterns of piston-engine aircraft and gather information on 

aircraft type (multi- and single-engine) via tail fin number30 

30 Modeling results suggest strong peaks in hourly concentrations due either to increased piston-engine aircraft 

activity or meteorological conditions. Properly characterizing these peak periods are likely critical to the overall 

daily as well as seasonal average. 

 72 
	 Use 2-minute ASOS on-site wind speed and wind direction data – these data may be particularly 

important to accurately reflect wind direction, particularly during low wind speed periods 

	 Use site-specific terrain and land use data following procedures as recommended in EPA’s 

AERMOD implementation guide 

	 Gather information on stationary sources within at least 20 km of the airport 

 73 
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 74 
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