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<br /> <br />Foothill Sanitary Landfill Page 24 of 52 San Joaquin County DPW - Solid Waste <br />Joint Technical Document Revised 01/05/2026 <br /> <br />interior of the landfill will be decommissioned. The pipe risers at the exterior perimeter of the <br />landfill will be accessible during the life of the landfill for inspection of the LCRS system. These <br />risers will enable devices such as cameras or cleanouts to be inserted into the LCRS system to <br />check for clogging or the removal of clogs, respectively. <br /> <br />Final designs for each module for sequential liner and LCRS construction will be <br />prepared and submitted for review and approval to the appropriate regulatory agencies prior to <br />construction. <br /> <br />Leachate will be pumped from sumps and returned to Subtitle D modules in accordance <br />with the WDRs. <br /> <br />5.5.4. Vadose Zone Monitoring Sump <br />Each of the LCRS sumps in the future modules will be designed with a vadose zone <br />monitoring system below the primary LCRS sump acting as a leak detection system. The <br />vadose zone monitoring sump will be excavated into the subgrade below the LCRS sump at the <br />lowest point of the module floor. The vadose zone monitoring system will be localized in this <br />area because the LCRS sump will be the only area where a potential constant head of leachate <br />will be present on the liner system. Access to the leak detection sump will be via a sideslope <br />riser pipe. The vadose zone sideslope riser pipe will be 6 in. diameter, HDPE SDR 11 pipe. <br />The liquid (if any) in the vadose zone monitoring sump will be manually monitored on a periodic <br />basis. Any liquids in the vadose zone monitoring sump will be removed with a pump via the <br />sideslope riser pipe with the appropriate type and size pump. <br />Containment in the vadose zone monitoring sump will be accomplished with the <br />following components (Figure 5-5), from bottom to top: <br />• Prepared subgrade <br />• A geosynthetic clay liner (GCL) providing a hydraulic conductivity of no greater <br />than 5 x 10-9 cm/s <br />• 60-mil thick HDPE, double-sided textured geomembrane <br />• 12-inch-thick vadose zone gravel providing a minimum hydraulic conductivity of <br />0.1 cm/s <br />• Geotextile filter.