COMPLIANCE INFO_FINAL INITIAL STUDY/MITIGATED NEGATIVE DECLARATION 5/25

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Memorandum March 25, 2025 Page 13 21202-23 North County Landfill_AQ_0307 condition, the conservatively estimated maximum emissions from the flare are below the Valley Air District’s thresholds of significance. Therefore, the impact associated with LFG-related criteria air pollutant emissions would be less than significant. 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: Attachments A and B. Exposure to Toxic Air Contaminants Project operation 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 above, the closest sensitive receptor 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 1). 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 haul route, a health risk assessment was conducted to estimate the incremental increase in cancer risk and chronic hazard index (HI) from exposure to DPM emissions from trucks in accordance with guidance from the Valley Air District 8 and the Office of Environmental Health Hazard Assessment (OEHHA).9 8 Joaquin Valley Air Pollution Control District (Valley Air District), 2015. Guidance for Assessing and Mitigating Air Quality Impacts (CEQA Guidance), March 19. 9 Office of Environmental Health Hazard Assessment (OEHHA), 2015. Air Toxics Hot Spots Program Guidance Manual for Preparation of Health Risk Assessments, May.