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grades of the interim final cover. As discussed in the Settlement Analysis, Interim Cover;Austin Road Landfall(GeoLogic Associates, April 2002), the grades are based on maintaining positive drainage once refuse is placed above the interim final cover. The interim final cover and, therefore,the base of northern portion of WMU FU-06 generally grades at 3 percent to the south. The post-settlement grades of the northern portion of WMU FU-06 are expected to remain at approximately two percent to the south. • Leachate collected in the northern portion of the cell that overlies the former Austin Road Landfill will be collected along the southern berm located along the southern boundary of the former Austin Road Landfill top deck and routed to a temporary leachate tank via a 3-inch dia. HDPE pipe. Once the southern portion of WMU FU-06 is approved for disposal by the RWQCB, the southern termination berm on the former Austin Road.Landfill top deck will be removed. The liner and LCRS in the northern and southern portions of WMU FU-06 will be connected and leachate routed to the sump in the southern portion of WMU FU-06. • Only Class III wastes will be placed in the northern portion of WMU FU-06. Class III refuse that will be placed in the northern portion of WMU FU-06 will be overlain with an interface liner on the south facing slope to separate it from the Class II wastes that will be placed in the southern portion of WMU FU-06. • The edges of the WMU FU-06 liner include termination berms that protect the edge of the liner (see Construction Drawings in Appendix A) and allow connection of the WMU FU-06 lining system to adjacent future WMUs.The berms also define the limits of waste placement. 2.3 Supported Lining System WMU FU-06 incorporates an interface linin system to separate Class H wastes to be laced in WMU rp g Y p p FU-06 from Class III wastes placed in adjacent portions of the landfill. The interface lining systems will be located in the southern portion of WMU FU-06, where the cell overlies the former Austin Road Landfill, and on the south facing slope of the refuse that will be placed in the northern portion. In addition, the connection bench between the WMU FU-06 northern and southern portions overlies refuse. 2.3.1 Analytical Method Because the interface lining systems overly refuse, settlement is an important element of the interface liner design. A lining system constructed over an existing landfill is potentially subject to differential settlements that may occur because of the variable compressibility of different wastes and/or the collapse or degradation of large objects within the landfill. Differential settlements in the subgrade of an interface liner could result in tensile strains at the surface of the liner system and could affect the drainage capacity of the lining system's LCRS. If the tensile strains within the liner exceed the tensile capacity of the lining material, tensile failure could develop. Under extreme conditions, tensile failure will reduce the effectiveness of the liner as a hydraulic barrier by providing a direct flow path through the lining system.Additionally, differential settlements could affect the slope at which the lining system had been constructed and could possibly result in the reversal of leachate drainage grades. If grads reversal takes place at the surface of a liner and LCRS, leachate will pond on the liner, and the potential for infiltration of the leachate into the underlying waste will increase. Typical designs of interface lining systems incorporate measures to bridge over potential voids occurring near the underlying waste surface, which may result from the collapse of a large object, WMU FU-06 2.2