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Foothill Sanitary Landfill Page 22 of 53 San Joaquin County DPW - Solid Waste Joint Technical Document Revised 6/09/2020 A base liner and leachate collection and removal system (LCRS) were installed in Module 1. The LCRS is a collection system with a drainage blanket, main drains or collection pipes, and lateral drains placed immediately above the base liner and extended up the excavation side slopes. The collected leachate drains to the low points of the module and then into a collection sump, from which the leachate is directly pumped and removed through sideslope riser pipes. The base liner LCRS consists of a 0.75-foot-thick gravel drainage blanket, ditches, and perforated collection pipes placed within the ditches to limit leachate head build-up and transmit leachate to the low points in the module for collection, as well as collection trenches at the lateral limits of modules. The sideslope LCRS is a geocomposite drainage material. Locations and details of the existing liner, LCRS and leachate collection sumps are shown in Figures 16 and 18 . . The most recent leachate volumetric data is provided in the 2019 Semi- Annual Groundwater and Surface Water Monitoring Report attached as Appendix K. 5.5.2. Future Leachate Collection System The LCRS for future modules will be similar to the system built for Modules 1 and 2. The maximum side slope excavations will be limited to 3:1. The base LCRS will be comprised of a 0.75-foot-thick gravel drainage layer with a minimum permeability of 0.1 cm/sec, or an approved alternative. Above the gravel drainage layer, a nonwoven geotextile will be placed to filter soil particles from the leachate as the leachate percolates through the overlying operations layer. The base of each module will be graded to provide a minimum 1.4 percent slope towards collection trenches. The trenches will be a 1-foot deep v-ditch with 3:1 (horizontal to vertical) side slopes, sloped at 1 percent towards a collection sump. In select instances, the slope of a collection trench may be reduced to accommodate the tie in of the individual LCRS trenches within a cell. This will allow the collected leachate to drain to one sump within the cell. This main collection trench would typically be located at the toe of an excavation slope where the waste fill over it is a near constant height. A constant height of waste over the trench produces consistent normal stresses that reduce the likelihood of subgrade differential settlement. Thus, the minimum slope will be maintained.