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ARROYO LAGO RESIDENTIAL PROJECT ADDENDUM FCS 77 Https://adecinnovations.sharepoint.com/sites/PublicationsSite/Shared Documents/Publications/Client (PN-JN)/2148/21480036/Addendum/21480036 Arroyo Lago Residential Project Addendum.docx c) Sensitive Receptors Would the project: Expose sensitive receptors to substantial pollutant concentrations? Prior FEIR Conclusions Sensitive receptors near the project site include residential neighborhoods directly adjacent to the west, less than 50 feet from the project site. The Prior FEIR evaluated potential exposure to toxic air contaminants (TACs), particularly diesel particulate matter (DPM) during construction. A construction- related Health Risk Assessment (HRA) was conducted, which determined that impacts could be potentially significant because cancer risk resulting from the construction of the County Project would exceed the Bay Area Air District’s project-level significance thresholds. As such, the County Project would be required to implement MM AIR-3, which includes the use of Tier 4 interim engines and preparation of a construction operations plan. These measures would reduce construction-related exposure to TACs for nearby sensitive receptors to a less than significant level. Construction and operational air emissions would be reduced under Alternative 2 because off-site utility improvements would not be built, resulting in a smaller total impact area and less disturbance. However, the same identified mitigation would still be required. In terms of operational impacts, the Prior FEIR determined that the County Project would not be a significant source of TAC, DPM, or carbon monoxide (CO). Additionally, the First Production Phase (in the northwest part of the project site) was assumed to start in October 2025 and be completed in late May 2026, when the first group of occupants would be expected to move into the completed houses; the surrounding vertical construction would continue until late August 2027. The Prior FEIR determined that the first group of occupants’ exposure to criteria pollutants would not exceed the Bay Area Air District health risk threshold from DPM generated during the subsequent 15 months of vertical construction; therefore, the DPM health risk impact for the first group of occupants would be less than significant, and operational impacts were also found to be less than significant. Criteria pollutant emissions would remain below significance thresholds, and required mitigation for fugitive dust and construction health risks would still apply. (Draft EIR, pp. 6-12–6-13). Therefore, the Prior FEIR concluded that impacts would be less than significant with mitigation incorporated. (Draft EIR, pp. 3.2-25, 6-12). Proposed Project Analysis and Conclusion The closest sensitive receptors to the project site include single-family residences located immediately to the west, less than 50 feet from the project site. Unlike regional emissions, localized emissions are typically evaluated in terms of air concentration rather than mass, so they can be more readily correlated to potential health effects. As described in the Prior FEIR, the cancer risk resulting from the construction of the County Project would exceed the Bay Area Air District’s project-level significance thresholds. The proposed project would be substantially similar to the County Project, though with fewer proposed dwelling units, in addition to a substantial reduction in off-site improvements, including the removal of the proposed water storage and booster pump facility, WWTP, recycled water storage, and agricultural irrigation fields from the