# Work Plan for Air Quality

Modeling and Monitoring of Lead Emissions from Piston-Engine

Powered Aircraft

U.S. Environmental Protection Agency

Office of Transportation and Air Quality

Contractor: 

# ICF Consulting

20091



## Project Background

Tetraethyl lead is used as an additive in aviation fuel for most piston-engine powered aircraft. The 2002 National Emissions Inventory (N EI) estimates that annual lead (Pb)

emissions from the use of these leaded aviation fue ls (commonly referred to as “avgas”) are 623 tons, or approximately 45 percent of the ai r emission inventory for lead.

Additional mobile sources of Pb include automobile brake wear, tire wear, and loss of Pb wheel weights to roadways. Lead is also present as a trace contaminant in gasoline and diesel fuel and is a component of lubricating oil.

In October 2006, the Environmental Protection Agenc y (EPA) received a petition from Friends of the Earth (FOE) requesting that the Agen cy make a finding that lead emissions from general aviation aircraft may reasonably be an ticipated to endanger public health and, following on that finding, take action to cont rol Pb emissions from piston-engine

aircraft. 1 EPA surveyed the available literature and found t hat there are few monitoring or modeling studies of Pb concentrations near airpo rts servicing piston-engine aircraft that operate on leaded aviation gasoline.

The primary purpose of this study is to develop and evaluate a modeling approach that can enhance inputs to EPA’s air quality model, whic h can then be used to model Pb emissions at general aviation facilities across the United States. The purpose of the monitoring analysis is to collect data that can be used to evaluate the performance of the modeling approach and to collect additional informa tion to evaluate the gradient in Pb

concentrations with distance from the emissions sou rce.

This document summarizes the air quality modeling a nd monitoring that is planned for 2009 at the Santa Monica City Airport. This work p lan is divided into three primary parts: overview of the location, description of the approach for the air quality modeling and description of the monitoring activities.



## Overview of Location

The Santa Monica City Airport (SMO) was identified as a representative location for this study primarily due to the intensity of piston-engi ne aircraft activity and availability of data from a previous lead monitoring study. Establ ished in 1919, the Santa Monica Airport is the oldest community airport operating i n Los Angeles County. The airport is one of the busiest single runway airports in the na tion. The airport occupies over 200 acres (0.81 square kilometers) situated at the sout heastern portion of the City of Santa Monica. The City’s southern boundary coincides wit h 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. Approximately 6,500 residents live within one kilom eter of the airport.

1 See www.epa.gov/otaq/aviation.htm for more information.

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Contact the EPA Docket Center’s P ublic Reading Room to view or receive a copy of this document.

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## Air Quality Modeling

Emission Inventory Development

The following section discusses the methodology for developing the aircraft lead emission inventory (the principal source of lead ai r emissions at the airport) along with

the source of information for Pb emissions from oth er mobile and stationary sources.

Piston-engine Aircraft Source : Emissions generated from aircraft operations at gen eral aviation airports are based on the amount of fuel consumed during the landing and take off cycle (LTO) and the amount of time aircraft spend in each mode of operation. The five modes which define the LTO cycle are approach, taxi/idle-in, taxi/idle-out, ta keoff and climb out. 2 Rotocraft (helicopter) display a slightly different sequence during the operating cycle; the modes which typify rotocraft operations are approach, idl e and climb out. Each aircraft operates under a varied timeline depending on the type of ai rcraft and operational characteristics of the airport. Therefore, observational time-in-m ode data will be collected for pistonengine aircraft at SMO. To quantify aircraft emiss ions, the Federal Aviation Administration (FAA) has incorporated into its airc raft emission model, Emissions and Dispersion Modeling System (EDMS) 5.1, fuel consump tion information by LTO cycle for six single-engine piston aircraft and two twin- engine piston aircraft. 3 Information on fuel consumption in each mode will be used to deter mine lead emission rates for each LTO mode for each engine/aircraft type that visit S MO, using the Airport-Specific lead emission methodology discussed in EPA’s Technical S upport Document on Lead

Emissions from the Use of Leaded Aviation Gasoline in the Untied States (October, 2008). 4

The aircraft activity and associated emissions will be aggregated to develop an hourly emission profile 5 to be used as input to AERMOD (a dispersion model used by EPA), with sets of profiles developed for each season and weekday/weekend. Leaded avgas fuel samples will be collected and analyzed for tot al Pb content so that site-specific fuel Pb concentrations are used in the development of th e aircraft inventory.

Other Mobile Sources : Emissions from on-road sources operating within and near the airport may contribute additional airborne lead emissions beyond those emi tted from piston-engine aircraft. The South Coast Air Quality Management District (SCAQMD ) recently completed their South Coast MATES-III air toxic modeling study whic h included the development of a

2 For the climb out and approach mode, we use the de finition consistent with other airport related emis sion analysis, which is a default mixing height of 3,000 feet or almost one kilometer.

3 EDMS available from http://www.faa.gov/about/office_org/headquarters_of fices/aep/models/edms_model/

4 U.S. EPA (2008) Technical Support document on Lead Emissions from the Use of Leaded Aviation

Gasoline in the Untied States. EPA-420-R08-202. Ava ilable at: http://www.epa.gov/otaq/aviation.htm.

5 SMO is closed to all aircraft activity between 11 pm and 7 pm except for emergency police helicopters

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lead emission inventory. 6 The emissions inventory for MATES III consists of four components: (1) point sources; (2) area sources; (3 ) on-road mobile sources; and (4) offroad (or other) mobile sources. Point source emiss ions are from facilities having one or more pieces of equipment registered and permitted w ith the SCAQMD. Area sources represent numerous small sources of emissions that can collectively have significant

emissions. On-road mobile sources include cars and trucks. All mobile sources not included in the on-road mobile source inventory are considered as off-road mobile sources, which include aircraft, ships, commercial boats, trains, recreational vehicles, and construction equipment.

Point Source Characterization : To fully characterize other sources which may contr ibute to ambient levels of lead, nearby point sources should be included in the anal ysis. Point sources up to 20 km in radius from the airport will be incorporated into t he analysis. Point sources will also be identified from comparison with the SCAQMD air perm it database point source emission inventory for lead which has supporting information on stack parameters (exit velocity, stack height, stack diameter, stack temperature).

Air Quality Analysis

The EPA AERMOD model will be used for the air quali ty analysis. This latest version of EPA’s air quality model has undergone extensive mod el testing and evaluation in recent years and represents the current state-of-the-scien ce and appropriate air quality model for assessing the potential emissions impacts on air qu ality from this facility. The model includes treatment for an urban nighttime boundary layer; applicability for all terrain types and a state-of-the-science approach for chara cterizing the fundamental boundary layer parameters and a treatment for plume meander as well as the inclusion of the stateof-the-science wet and dry deposition model.

AERMOD will be run using one year of nearby represe ntative on-site meteorological data from the SMO monitoring site. The Automated S urface Observation System (ASOS) monitoring site is located at the airport. The AERMET preprocessor model will be used to develop the meteorological dataset for u se with AERMOD.

Point sources will be modeled using standard point source information on location, stack height, stack diameter, exit velocity and temperatu re. As available, we will include information on the hourly variability in these emis sion rates. Area and mobile source emissions as obtained from the MATES-III study by c ategory emission source (CES) code will be included as gridded area sources. All aircraft-related emission sources will

be modeled as volume sources.

6 South Coast Air Quality Management District, Multi ple Air Toxics Exposure Study-III (MATES III) July 2008. Available at: http://www.aqmd.gov/prdas/mate sIII/matesIII.html5

Receptor Sites

Maximum Receptors: The selection of receptors in AERMOD to find the ma ximum lead concentration will employ a nested Cartesian grid with receptors space d 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 will be placed at 50 meter intervals arou nd the airport boundary fence line. In addition, site-specific sensitive receptor location s will also be included within 2 kilometers of the airport. Types of sensitive rece ptors include playgrounds, schools, and
recreational areas.

Sensitivity Analysis: A model sensitivity analysis will be conducted focu sing on those parameters most uncertain in the analysis. This will provide infor mation on the relative importance of these parameters to the overall lead concentration as well as providing information on the relative value in obtaining more detailed site-spec ific information.

Sensitivity analysis will be conducted for the wors t 3-month period identified from the one-year of modeling. At a minimum, the sensitivit y tests will include the parameters: fuel consumption and time-in-mode.



## Monitoring Activities

The monitoring activities will include: collection of air samples, soil samples and dust samples from areas in and around SMO. The primary purpose of the air monitoring is to provide data for comparison with AERMOD air quality data. Soil and dust samples will be collected to evaluate the potential for a gradie nt in Pb concentrations in soil with distance from the airport. Dust samples will be co llected at various receptor sites to evaluate a potential impact of Pb from piston-engin e aircraft emissions.

Ambient Air Monitoring Plan

Air samples will be located at a maximum of six loc ations on and around the airport property to attempt to both evaluate the concentrat ion at the most highly impacted location and to evaluate the gradient in lead conce ntrations with distance from the airport. In the study conducted at SMO in 2005-2007 by SCAQM D, air monitoring was conducted at seven locations, the data from which w as used to inform monitoring sites for this project. 7

7 South Coast Air Quality Management District, Phili p M. Fine. Community-Scale Air Toxics Monitoring – Sun Valley Neighborhood and General Aviation Airpor ts. Presented at the U.S. EPA Air Toxics Data Analysis Workshop - Chicago, IL October 2 - 4, 2007

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Air sampling is planned for the summer of 2009. Th e sample period will run approximately seven days. The prevailing air flow throughout the annual cycle is onshore from the southwest. Air samples will be co llected at a location that is in the prevailing upwind direction of the airport and in t he prevailing downwind direction. In this study, we are planning to collect air samples in the community directly downwind of the runway and/or run-up areas.

Soil and Dust Sampling Plan

Soil Sampling: Soil samples will be collected from a minimum of ei ght areas on or near airport property, including an elementary school and homes. Sampling areas are being selected based on a number of factors, including: proximity to take-off and landing areas, availability of relatively undisturbed and non-vegetated surficial earth materials, and accessibility. The sampling program is designed to gather data on the presence and distribution of total lead in bulk soil samples (i.e., present throughout the soil matrix) and in the fine-grained components of a bulk sample. It is the fine-graine d 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.

Dust Sampling: Dust sampling is commonly used to assess the deposi tion of air-borne contaminants on surfaces. A minimum of ten dust samples will be co llected from areas on and near airport property, including playground areas and ho mes. In addition, approximately five controlled dust samples will be collected in homes. A controlled dust sample will be collected from surfaces that have been pre-cleaned to remove any residual material. After a period of at least seven days, the dust acc umulated on the surface will be

collected.



### Timeline and Contact Information

The study will be completed by October 2009. When available, the final report will be posted at www.epa.gov/otaq/aviation.htm

.

For additional information please contact:

Meredith Pedde Marion Hoyer Environmental Protection Agency Environmental Prot ection Agency Office of Transportation & Air Quality Office of T ransportation & Air Quality

2000 Traverwood Dr. 2000 Traverwood Dr. Ann Arbor, MI 48105 Ann Arbor, MI 48105

734-214-4748 734-214-4513 pedde.meredith@epa.gov hoyer.marion@epa.gov