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 41 not change the North County Landfill design capacity, the rate of additional cell and module construction on the project site would increase to accommodate the amount of waste accepted with the proposed increase in maximum allowed daily refuse disposal. Compared to the current operation conditions, the project could increase the rate of LFG generated and collected but is not expected to substantially change the total amount of LFG generated over the lifetime of the landfill since the total waste-in-place would remain the same once landfill capacity is reached. The long-term LFG emissions of methane for the North County Landfill were estimated using the EPA Landfill Gas Emission Model (LandGEM) version 3.1 and AP-42 default inputs. Information about historical waste acceptance rates (1991 to 2023), closure year (project condition), and predicted annual increases in waste intake were provided by the applicant. For the baseline condition, it was assumed that 250,000 tons of waste was accepted in 2024, and a three percent increase in waste disposal rate per year thereafter. Under this scenario, the North County Landfill would reach the 20.6 million tons design capacity by 2059. For the project condition, it was assumed that the waste disposal rate would increase from 250,000 tons in 2024 to 660,000 tons in 2026, then a three percent increase in waste disposal rate per year thereafter. Under this scenario, the North County Landfill would reach the 20.6 million tons design capacity by 2043. As described above, LFG-derived CO2 emissions (including CO2 from combustion of methane at the flare) are considered biogenic, part of the natural carbon cycle and are not considered an anthropogenic contributor to climate change; therefore, the biogenic CO2 emissions from LFG are not included in the evaluation of the project’s potential impacts on climate change from GHG emissions. Methane content in the LFG was assumed to be 50 percent. Although the North County Landfill has a landfill gas collection system, those systems are not 100 percent efficient in collecting LFG and hence fugitive emissions of methane would still occur. With the absence of site-specific data, LFG collection system collection efficiencies, which are subject to landfill cover type, were obtained from 40 CFR Part 98 subpart HH. The North County Landfill is only partially built and as such all cover on the site is either daily or intermediate cover. Construction of final covers is planned to be done in conjunction with the excavation and construction of future modules. According to the North County Landfill Joint Technical Document revised in 2024, 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 covered 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. 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 project’s estimated net increase in average annual GHG emissions from operation would total approximately 2,537 metric tons CO2e in 2026. GHG emissions from off-road equipment and landfill methane emissions would increase with the implementation of the project due to the