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ARROYO LAGO RESIDENTIAL PROJECT ADDENDUM FCS 75 Https://adecinnovations.sharepoint.com/sites/PublicationsSite/Shared Documents/Publications/Client (PN-JN)/2148/21480036/Addendum/21480036 Arroyo Lago Residential Project Addendum.docx b) Cumulative Criteria Pollutant Emissions Impacts Would the project: Result in a cumulatively considerable net increase of any criteria pollutant for which the project region is nonattainment under an applicable federal or State ambient air quality standard? Prior FEIR Conclusions The Prior FEIR found that the SFBAAB is in nonattainment for ozone (O3), particulate matter less than 2.5 microns in diameter (PM2.5), and particulate matter less than 10 microns in diameter (PM10). The County Project would generate emissions during construction and operation, including criteria pollutants such as nitrogen dioxide (NO2), carbon monoxide (CO), sulfur dioxide (SO2), and particulate matter. Emissions modeling was conducted using the California Emissions Estimator Model (CalEEMod) and assumed implementation of MM AIR-1, which includes dust control, equipment maintenance, and idling restrictions. With respect to construction-related impacts, the Prior FEIR determined that MM AIR-1 would be required to reduce construction-related criteria pollutant impacts to less than significant levels because the Bay Area Air District requires implementation of its BMPs for construction dust as a qualitative criterion for determining CEQA significance. Operational emissions were also evaluated and found to be below the Bay Area Air District thresholds, and therefore, mitigation was not triggered. Therefore, the Prior FEIR concluded, with respect to criteria air pollutants, that construction-related impacts would be less than significant with mitigation incorporated, and operational-related impacts would be less than significant. (Draft EIR, pp. 3.2-50, 6- 12, 6-13). Proposed Project Analysis and Conclusion This impact is related to the cumulative effect of a project’s regional criteria pollutant emissions. By its nature, air pollution is largely a cumulative impact resulting from emissions generated over a large geographic region. The nonattainment status of regional pollutants results from past and present development within the Air Basin, and this regional impact is a cumulative impact. Therefore, new development projects (such as the proposed project) within the Air Basin would contribute to this impact only on a cumulative basis. No single project would be sufficient in size, by itself, to result in nonattainment of regional air quality standards. Instead, a project’s emissions may be individually limited, but cumulatively considerable when evaluated in combination with past, present, and future development projects. The HRA conducted in the Prior FEIR conservatively assumed that construction would occur seven days per week. A more realistic scenario involves a 5-day workweek while maintaining the same total number of construction days, thereby extending the overall schedule in calendar time. Under Office of Environmental Health Hazard Assessment (OEHHA) guidance, chronic risk estimates (cancer risk and hazard quotients) are based on total cumulative exposure over time. Because the total number of construction days—and thus total emissions—would remain unchanged, chronic risk results are not expected to differ materially.