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LCRS Design - Area 26 Foothill Sanitary Landfill design leachate generation rate by a factor greater than 2 while limiting the hydraulic head on the liner to well under 12 inches (less than the thickness of a GDN). GDN design calculations are discussed in Section 5 of this report. The County has indicated to GLA that they may, at some point in the future, pursue approval for an increased final filling elevation at the FSLF. As such, GLA has analyzed the required GDN transmissivity for waste fills up to 300 feet thick. If the County does anticipate waste filling to 300 feet of thickness the minimum 100-hour transmissivity of the GDN should be 3.5x10-4 mz/s at a vertical stress of 25,000 psf, and no testing should be required at 11,000 psf vertical stress. The minimum 100-hour transmissivity at 1,000 psf vertical stress remains the same. Blanket drainage layer model output and calculations are provided in Attachments 1 and 2 of this report. 3.2 Side-Slope LCRS Similar to previous module designs, the side-slope LCRS drainage layer was designed with a relatively steep inclination as compared to the floor of the area. Specifically, Area 2B will have a minimum slope of 33.3% (3H:1V) to the base LCRS. The side-slope LCRS will be comprised of double-sided GDN draining to collector pipes at the toe of the slopes. Blanket drainage layer calculations are provided in Attachment 2 of this report. 3.3 LCRS Collection Pipe Perforated HDPE leachate collection pipes will be placed within a gravel wrap located in a trench below the GDN and will run along the floor of Area 2B to convey leachate to the LCRS sump. The LCRS pipe network consists of 6-inch diameter lateral pipes and 6-inch diameter header pipes. All piping is capable of conveying more than two times the predicted peak daily flow of leachate. All LCRS collection pipes will be rated SDR 9. Calculations for flow capacity and pipe strength are included in Attachment 3 of this report. 3.4 LCRS Sump Area 2B was designed with a single sump located in near the southeastern side of the cell. The sump has approximate dimensions of 70 feet x 70 feet x 4 feet deep, and will be filled with granular material. The sump was designed to accommodate only leachate from Area 2B. The design is similar to that used on Area 2A as designed by Geosyntec. A primary sump with risers will include two 24-inch diameter HDPE pipes, one as a primary access pipe and another as a secondary access pipe, along with 6-inch-diameter instrumentation pipes for each access pipe. A permanent submersible pump will be installed in the primary riser pipe to pump out leachate. To allow for the removal of the pump without removing the instrumentation or sensor, instrumentation pipes will be included next to each sump riser (i.e. the primary and the secondary). Underneath the primary sump, a secondary sump with 12-inch diameter HDPE pipe and riser and 6-inch-diameter instrumentation pipe will be installed. A temporary submersible pump will periodically be lowered into the secondary sump to check for liquid. Project No. AU 17.1254 1 LCRS Design 3 May 2018