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North County RC&SL Page 8 of 64 Public Works/Solid Waste <br />Joint Technical Document County of San Joaquin – Revised July 14, 2025 <br />2.3.1 Landfill Gas (LFG) <br />2.3.1.1 Landfill Gas Migration Monitoring and Control <br />The monitoring perimeter (which excludes the “Martin Residence” structures) and on-site <br />structures are monitored in accordance with the Landfill Gas Monitoring and Control Plan <br />(Appendix I). Migration monitoring is provided by eighteen perimeter monitoring wells. These <br />wells include three sampling intervals in accordance with California Code of Regulations (CCR) <br />Title 27 Article 6. The site was in full compliance with these regulations. <br /> <br />Subsurface migration is controlled by the LFG system which was installed in 2006. This system <br />is operated in accordance with San Joaquin Valley Air Pollution District permit N-1119. The <br />system consists of vertical wells, horizontal collectors and is also connected to some of the <br />leachate risers. Additional wells and collectors are installed as the landfill develops. <br /> <br />2.3.1.2 Landfill Gas Emissions Control <br />Surface emissions are controlled by the LFG collection and treatment (flare) system described <br />above. Collected LFG is combusted in a temperature-controlled flare (Plate 2). A new Low NOx <br />flare was in September 2024. The new flare will become the primary treatment device while the <br />existing flare will remain as a backup unit. <br /> <br />2.3.2 Leachate <br />2.3.2.1 General <br />Leachate is liquid that is collected in the leachate collection system. Leachate from MSW is a <br />mixture of soluble organic and inorganic constituents, suspended solids, and bacteriological <br />constituents. Leachate is primarily a result of rainwater infiltrating through the waste mass and <br />waste decomposition. <br /> <br />In general, the rate of leachate generation at a landfill is highest early in the operating life of the <br />facility. The long-term reduction in leachate generation is due to final cover placement and low <br />permeability of the cover. <br /> <br />The quantity of leachate generated in MSW landfills is dependent on the following factors: