COMPLIANCE INFO_FINAL INITIAL STUDY/MITIGATED NEGATIVE DECLARATION 5/25

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Memorandum 25 March 2025 Page 12 According to the North County Landfill Joint Technical Document revised in 2024,8 a final cover for a portion of the landfill is proposed by 2029. Therefore, it was assumed that most of the landfill areas are covered by intermediate cover between 2024 and 2029 (collection efficiency 65 percent), then 50 percent of the landfill areas will be cover by a final cover between 2030 and the closure year (weighted average collection efficiency 75 percent). After the closure year, it was assumed that all landfill areas will be covered by a final cover (collection efficiency 85 percent). In addition, it was assumed that 10 percent of the fugitive methane emissions are oxidized to CO2 as the gas passes through the landfill soil cover.9 The collected LFG would be combusted in a temperature-controlled flare. During combustion, gaseous hydrocarbons react with atmospheric oxygen to form CO2 and water. The destruction efficiency is defined as the percentage of a specific pollutant in the flare vent gas that is converted to a different compound (such as CO2). Methane destruction efficiency for the flare was assumed to be 99 percent based on the Title V Permit. The input parameters, assumptions, LandGEM outputs, and associated calculations for estimating LFG derived methane emissions are provided in Attachment A. As shown in Table 1, the project’s estimated net increase in average annual GHG emissions from operation would total approximately 2,537 metric tons CO2e in year 2026. GHG emissions from off-road equipment and landfill methane emissions would increase with the implementation of the project due to the increase waste intake and associated landfill operations. However, GHG emissions from on-road mobile sources would decrease by 230 metric tons CO2e per year, mainly attributable to the shorter truck trip distance of the re-routed trucks. It is to be noted that GHG emissions from off-road and on-road mobile sources in later years would be lower due to the increasingly stringent emissions standards and fleet turnover (including construction off-road equipment, trucks, and on-road passenger vehicles). Table 1. Estimated Annual GHG Emissions (metric tons CO2e per year) Emission Scenarios Off-Road Equipment On-Road Mobile Sources Landfill Methane Emissions Total Baseline Condition 1,115 4,354.4 40,933 46,463 Project Condition (As of 2026) 1,978 4,124.7 42,898 49,000 Net Difference 863 -230 1,904 2,537 Source: Attachment A. 8 San Joaquin County Public Works, 2024. Joint Technical Document for North County Recycling Center and Sanitary Landfill. August 30. 9 U.S. EPA, 2020. Documentation For Greenhouse Gas Emission and Energy Factors Used in the Waste Reduction Model (WARM). Management Practices Chapters. November. https://www.epa.gov/sites/default/files/2020- 12/documents/warm_management_practices_v15_10-29-2020.pdf.