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5.0 Environmental Analysis 5.5 Air Quality Avion Project SEIR Page 5.5-1 5.5 Air Quality This section evaluates potential short-term (construction) and long-term (operational) air quality and odor impacts associated with the project. The following discussion is based on the Air Quality Analysis (RECON 2019d) prepared by RECON and included as Appendix D. 5.5.1 Relationship to the Black Mountain Ranch (Subarea I) Subarea Plan The analysis in this section updates the air quality analysis in the 1998 Environmental Impact Report (EIR), with an emphasis on effects that were not addressed in the previous report. Because no site- specific design was proposed at the time the 1998 EIR was prepared, impacts relative to construction emissions, including blasting impacts, could not be analyzed in detail for the perimeter properties. Cumulative construction-related air quality impacts were considered to be potentially significant. Operational air quality impacts were adequately analyzed as part of the 1998 EIR, to which this Supplemental Environmental Impact Report (SEIR) is tiered. Those impacts are summarized in Chapter 9.0. 5.5.2 Existing Conditions 5.5.2.1 Project Site The existing site is undeveloped and primarily covered with vegetation. The site is comprised of a central ridge that rises in elevation towards the south bounded by small canyons with drainage courses to the east and west, with a dirt road located along the crest of the ridge. As the project site is undeveloped, it is currently not a source of criteria pollutant emissions. 5.5.2.2 Regional The project site is in the San Diego Air Basin (SDAB), which lies in the southwest corner of California and comprises the entire San Diego region. Population and emissions are concentrated mainly in the western portion of the county. The SDAB covers 4,260 square miles, includes about 8 percent of the state’s population, and produces about seven percent of the state’s criteria pollutant emissions. The City of San Diego covers approximately 330 square miles, or 8 percent, of the SDAB. Air quality at a given location is a function of the types and quantities of pollutants being emitted into the air locally and throughout the basin, and the dispersal rates of pollutants within the region. The major factors affecting pollutant dispersion are wind speed and direction, the vertical dispersion of pollutants (which is affected by inversions), and the local topography. Air quality in the SDAB is impacted not only by local emissions but also by pollutants transported from other areas, in particular, ozone and ozone precursor emissions transported from the South Coast Air Basin and Mexico. Although the impact of transport is particularly important on days with high ozone concentrations, transported pollutants and emissions cannot be blamed entirely for the ozone