COMPLIANCE INFO_FINAL INITIAL STUDY/MITIGATED NEGATIVE DECLARATION 5/25

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North County Recycling Center and Sanitary Landfill Permit Revision Project Final Initial Study/Mitigated Negative Declaration · San Joaquin County | May 2025 24 Table 3. Estimated Annual Criteria Air Pollutant and Precursor Emissions from Permitted LFG Collection System (tons per year) EMISSION SCENARIO EMISSIONS (TONS PER YEAR) ROG2 NOx PM10 CO SOx Baseline Condition1 <0.01 0.04 0.09 <0.01 0.02 Project Condition 1.41 6.41 3.63 9.62 3.21 Net Difference 1.41 6.37 3.54 9.62 3.19 Valley Air District Thresholds 10 10 15 100 27 Threshold Exceeded? No No No No No 1 Based on 2023 inventory for the North County Landfill. 2 ROG emissions based on total VOC emissions. Source: Appendix A, Attachments B and C. Therefore, the project would not result in a cumulatively considerable net increase in any criteria air pollutant for which the region is in nonattainment, or for LFG. The impact would be less than significant. c) Expose sensitive receptors to substantial pollutant concentrations? Less-than-Significant Impact Exposure to Toxic Air Contaminants Operation of the project would generate LFG-related emissions and DPM emissions from the exhaust of on-road heavy-duty diesel haul trucks and on-site off-road diesel construction equipment. As discussed in the Environmental Setting section above, the closest sensitive receptor to the landfill is a residence located on-site approximately 2,100 feet northeast from the top of Lined Area 1, and approximately 1,800 feet northeast from the existing LFG flare station (Figure 5). Because the closest sensitive receptor is not located within 1,000 feet of the fill area and flare station, exposure to on-site TACs during project operation was not evaluated. Although LFG may contain trace amount of TACs, the health risk from flare emissions is typically very low as the combustion process would destroy most toxic substances contained in the flared gas. Per the project’s Title V permit, VOC destruction efficiency for the flare shall be at least 98 percent by weight. For sensitive receptors along the truck haul route, a health risk assessment was conducted to estimate the incremental increase in cancer risk and chronic hazard index from exposure to DPM emissions from trucks. This assessment followed guidance outlined by the Valley Air District and the Office of Environmental Health Hazard Assessment (OEHHA) (Valley Air District 2015, OEHHA 2015). The on-road DPM emissions from trucks travelling by sensitive receptors along the haul route were estimated based on the net increase in average daily truck trips in the project vicinity. Emission data was taken from CARB’s database, and air quality models were used to estimate DPM concentrations along the route. Based on the annual average concentrations of DPM estimated using air dispersion modeling, potential health risks were evaluated for the maximally exposed individual resident (MEIR), which represents the most sensitive individual who could be exposed to adverse air quality conditions in the vicinity of the haul route.