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<br /> <br />Foothill Sanitary Landfill Page 22 of 52 San Joaquin County DPW - Solid Waste <br />Joint Technical Document Revised 01/05/2026 <br /> <br />5.5. Leachate Collection and Recovery System <br /> <br />5.5.1. Existing Leachate Collection System <br />This section has been revised to expand on the same section presented in the 2020 <br />JTD. Module “I”, the existing unlined landfill area, was not constructed with leachate control and <br />monitoring systems. Leachate control will be implemented, in part, by placing final cover on <br />sections of Module “I” as they reach final grade. <br /> <br />A base liner and leachate collection and removal system (LCRS) were installed in <br />Module 1. The LCRS is a collection system with a drainage blanket, main drains or collection <br />pipes, and lateral drains placed immediately above the base liner and extended up the <br />excavation side slopes. The collected leachate drains to the low points of the module and then <br />into a collection sump, from which the leachate is directly pumped and removed through <br />sideslope riser pipes. <br /> <br />The base liner LCRS consists of a 0.75-foot-thick gravel drainage blanket, ditches, and <br />perforated collection pipes placed within the ditches to limit leachate head build-up and transmit <br />leachate to the low points in the module for collection, as well as collection trenches at the <br />lateral limits of modules. The sideslope LCRS is a geocomposite drainage material. <br /> <br />Locations and details of the existing liner, LCRS and leachate collection sumps are <br />shown in Figures 16 and 18. The most recent leachate volumetric data is provided in the 2025 <br />Semi-Annual Groundwater and Surface Water Monitoring Report attached as Appendix K. <br /> <br />5.5.2. Future Leachate Collection System <br />The LCRS for future modules will be similar to the system built for Modules 1 and 2. The <br />maximum side slope excavations will be limited to 3:1. The base LCRS will be comprised of a <br />0.75-foot-thick gravel drainage layer with a minimum permeability of 0.1 cm/sec, or an approved <br />alternative. Above the gravel drainage layer, a nonwoven geotextile will be placed to filter soil <br />particles from the leachate as the leachate percolates through the overlying operations layer. <br />The base of each module will be graded to provide a minimum 1.4 percent slope towards <br />collection trenches. The trenches will be a 1-foot-deep v-ditch with 3:1 (horizontal to vertical)