Guidebook for Quantifying Airport Ground Access Vehicle Activity for Emissions Modeling (2017)

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5 C H A P T E R 2 The emissions from GAV are categorized as being air pollutants (i.e., emissions for which National Ambient Air Quality Standards [NAAQS] exist); air pollutant precursors (i.e., emissions which secondarily form into air pollutants); hazardous air pollutants (HAPs), and greenhouse gases (GHGs). This chapter presents an overview of the computer models that are used to derive airport GAV emission rates to prepare inventories of the pollutants, precursors, HAPs, and GHGs, and to prepare estimates of pollutant concentrations. More specific information per- taining to each model’s applications, design features, input and output data, and other func- tional parameters is available in the Contractor’s Final Report for ACRP Project 02-63. 2.1 Emissions Rate Models The MOVES and EMFAC models are the requisite software for computing on-road motor vehicle emissions factors throughout the United States. MOVES can be used to estimate motor vehicle emissions for any part of the United States except California. Emission rates for vehicles in California are estimated using the EMFAC model. By definition, on-road motor vehicles are designed and equipped to travel on public roadways and generally comprise automobiles (e.g., passenger cars, vans, motorcycles, etc.), buses, and trucks. The MOVES model provides both a total emissions inventory as well as emission rates by vehicle type, fuel type, and other factors. At publication of this guidebook, the latest version of the model is MOVES2014a (see box). For simplified projects/assessments being performed for airports in California, commonly used EMFAC emission rates can be obtained from CARB’s web database. More complex studies, which require hourly emissions or emission rates data by temperature and humidity, are obtained from the EMFAC model. Computer Models MOVES and EMFAC • Additional information about the U.S. EPA MOVES software can be obtained at: https://www3.epa.gov/otaq/models/moves/index.htm. MOVES2014a, released in October 2014, became the required model as of October 7, 2016 (79 FR 60343). • Additional information about the CARB EMFAC software/web database can be obtained at: https://www.arb.ca.gov/msei/msei.htm. The EMFAC2014 model and web-based database (current version 1.0.7), were approved for regulatory planning inventories by the EPA in December 2015 (79 FR 60343).

6 Guidebook for Quantifying Airport Ground Access Vehicle Activity for Emissions Modeling AEDT • The current version, AEDT2c, was released September 12, 2016. • Additional information about the AEDT can be obtained at: https://aedt.faa.gov/. AERMOD and CAL3QHC/CAL3QHCR • Additional information on the AERMOD model is available at: https://www3. epa.gov/ttn/scram/dispersion_prefrec.htm#aermod. • Additional information about the CAL3QHC/CAL3QHCR software can be obtained at: https://www3.epa.gov/ttn/scram/dispersion_prefrec.htm#cal3qhc. Both MOVES and EMFAC are applied in the “project-level” mode to derive an emission inventory for an airport. In project-level mode, the models produce emission rates (i.e., mass emissions per unit activity). These emission rates are combined with corresponding activity data to produce emission inventory totals. 2.2 Dispersion Models FAA’s AEDT is the required model for performing air quality analyses for airport-related emis- sion sources, including GAV operating on airport roadways, curbsides, parking facilities, and so forth (see box). For the purpose of modeling dispersing pollutants, the AEDT contains the AERMOD model. AERMOD is the EPA-preferred atmospheric dispersion model for assessing a wide assortment and combinations of stationary and mobile sources of emissions. The current AEDT release does not include GAV-related sources (e.g., roadways and parking lots). For these sources, emissions are evaluated externally through MOVES and then imported into AEDT. As such, the data requirements for AEDT to prepare an emissions inventory are the same as the requirements described above for MOVES and EMFAC. It is FAA’s intent that future releases of the AEDT model will include a roadway network design feature that will allow analysts to geographically define roadway links, parking lots and construction areas on airport property. Analysts will then export the roadway network information, model the emissions with MOVES for the sources that are defined using AEDT, and then import the emissions into AEDT (i.e., GAV emissions will still be evaluated externally through MOVES). 2.3 Hot-spot Models Assessment of some airport improvement projects that involve GAV may require air pollutant “hot-spot” analysis. (Hot-spots are localized areas of elevated pollutants such as roadway inter- sections, terminal curbsides, parking garages, etc.) Two EPA-developed computer models can be used for this purpose: CAL3QHC and CAL3QHCR. The CAL3QHC model was developed to predict pollutant concentrations of carbon monoxide (CO) and other inert pollutants from motor vehicles approaching and departing roadway intersections. CAL3QHCR, a more refined version of this model, requires local meteorological data and may be considered on a case-by- case basis. In July 2015, EPA proposed to replace CAL3QHC and CAL3QHCR with AERMOD as the preferred dispersion model for all mobile source modeling of inert pollutants (see box).