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<br /> <br /> <br />Memorandum <br />March 25, 2025 <br />Page 9 <br />21202-23 North County Landfill_AQ_0307 <br />SIGNIFICANCE CRITERIA <br />Based on Appendix G of the CEQA Guidelines, implementation of the proposed project would <br />result in a significant air quality impact if it would: <br />1) Conflict with or obstruct implementation of the applicable air quality plan; <br />2) Result in a cumulatively considerable net increase of any criteria pollutant for which the <br />project region is nonattainment under an applicable federal or state ambient air quality <br />standard; <br />3) Expose sensitive receptors to substantial pollutant concentrations; or <br />4) Result in other emissions (such as those leading to odors) adversely affecting a <br />substantial number of people. <br />The thresholds of significance for criteria air pollutant emissions, TACs, and odor established by <br />the Valley Air District are used in this study to evaluate the project’s air quality impacts. For <br />criteria air pollutants, the Valley Air District established these thresholds of significance based <br />on District New Source Review offset requirements for stationary sources, with the resulting <br />emission reductions playing a critical role in the Valley Air District’s air quality plans. Thus, <br />projects with emissions below the thresholds of significance for criteria pollutants are <br />determined to not conflict with or obstruct the implementation of the Valley Air District’s air <br />quality plan. For localized air quality impacts, such as exposure to TACs, the potential for <br />adverse air quality impacts decreases as the distance between the source of emissions and <br />receptors increases. The Valley Air District has not established a specific zone of influence <br />within which health risks to sensitive receptors must be analyzed. However, the Bay Area Air <br />Quality Management District recommends evaluating project’s potential health risks to <br />sensitive receptors within 1,000 feet of the project site. <br />Air districts such as the Valley Air District use regional air dispersion models to evaluate regional <br />criteria air pollutants. However, these dispersion models have limited sensitivity to the <br />relatively small (or negligible) changes in criteria air pollutant concentrations associated with an <br />individual project. Therefore, providing reliable estimates of specific health risks associated <br />with regional air pollutant emissions from an individual project is not feasible and would result