Item 27 - Appeal Application Nos. 2020-03 and 2020-04 - Central Pointe Mixed-Use Development

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3 SOURCE CHARACTERIZATION In urban communities, vehicle emissions contribute significantly to localized concentrations of air contaminants. Typically, emissions generated from these sources are characterized by vehicle mix, the rate pollutants are generated during the course of travel and the number of vehicles traversing the roadway network. Currently, emission factors are generated from a series of computer based programs to produce a composite emission rate for vehicles traveling at various speeds within a defined geographical area or along a discrete roadway segment. To account for the emission standards imposed on the California fleet, the ARB has developed the EMFAC2017 emission factor model. EMFAC2017 was utilized to identify pollutant emission rates for total organic gases (TOG), diesel particulates, particulates (PM10 and PM2.5), carbon monoxide (CO) and nitrogen oxide (NOx) compounds (2). To produce a representative vehicle fleet distribution, the assessment utilized ARB's Orange County population estimates for the 2020 calendar year. This approach provides an estimate of vehicle mix associated with operational profiles at the link or intersection level. Table 3-1 lists the identified fleet mix considered in the assessment. Based upon the freeway traffic volumes and population profiles noted above, discrete traffic counts were identified for each roadway segment. Diesel vehicles account for 3.94 percent of the total on -road mobile fleet. For chronic (long term) exposures, AADT values were averaged to produce representative hourly traffic volumes. An average observed route speed of 65 miles per hour was assumed for vehicles traversing the main highway link (1-5). The focus of this HRA is on DPM associated with vehicular activity traversing 1-5. Appendix 3.1 presents the on -road emission rate calculation worksheets for the freeway segment considered in the assessment.