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but are approximately 30 to 40 feet below amsl. According to the San Joaquin <br /> County Flood Control District, the historic high groundwater elevation is <br /> approximately 10 feet below amsl. If the historic high were to occur, a waste to <br /> groundwater separation of approximately 17 feet would be maintained. Given the <br /> effectiveness of the base lining system and the minimum 17-foot separation <br /> between the base of the WMU and groundwater, the lowered base grades exceed <br /> the technical and regulatory objectives for groundwater and waste separation. <br /> 5.2.2 LINER AND LCRS COMPONENTS <br /> The liner and LCRS system for the existing Forward Landfill were previously <br /> described in Section 4.1.1. A base liner and slope liner system are presented <br /> below for the future Forward Landfill. The existing Austin Road Landfill does not <br /> have a liner/LCRS system. An intermediate liner system is required over the <br /> existing refuse fill to separate Class III from Class II waste. That system is also <br /> described herein. <br /> 5.2.2.1 BASE LINER SYSTEM <br /> The base liner system design included in this JTD is based on compliance with <br /> the current WDRs for the existing facilities and in accordance with 27 CCR, <br /> Section 20330 requirements for a Class 11 liner system applicable to the Forward <br /> Landfill. Forward Inc. is currently in the process of working with the RWQCB to <br /> prepare a Liner Performance Demonstration for final determination of the base <br /> liner design. The current proposed base liner components for the Forward <br /> Landfill consist of (from bottom to top) (see Details 1 and 4 on Drawing 6): <br /> • Prepared subgrade; <br /> • A 24-inch thick low-permeability soil (minimum permeability of 1 x 107 <br /> cm/sec);' <br /> • A 60-mil high density polyethylene (HDPE) liner (textured); <br /> • A 12-ounce/square yard cushion geotextile (which can be omitted provided <br /> the LCRS is sub-angular to rounded); <br /> • A 12-inch LCRS gravel layer; <br /> • An 8-ounce/square yard separator geotextile; and <br /> • A 12-inch thick protective cover soil layer. <br /> A GCL may be used as part of a double composite liner in sump areas. <br /> Forward Landfill)TD 5-2 <br /> L\Allied\2000.193\ReportsUTD-PC PC MP702:Sec-5.0:5/'4/02 <br /> Revision 1:07/16/02 <br /> BRYAN A.STIRRAT&ASSOCIATES <br />