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5-1 0 5.0 DISPOSAL SITE DESIGN 5.1 Introduction The following section describes the proposed disposal site design features for the Forward Landfill, including the refuse fill areas, surface water drainage control system, LCRS, and the landfill gas control/ recovery systems. All of the environmental control systems have and will be installed to protect the environment and to comply with applicable regulatory requirements. This section also includes information regarding supporting design calculations for the Forward Landfill. 5.2 Design Plans All of the engineering design plans presented in this JTD are conceptual in nature and have been prepared using acceptable engineering practices. These plans are subject to change, including, but not limited to, regulatory changes and/or actual field conditions. Detailed design plans will be prepared for the various improvements and phases of development prior to construction. Any changes of substance proposed in detailed design plans will be reflected in an amendment to the JTD and submitted to the LEA, CalRecycle and RWQCB. The Forward Landfill has been designed under the direction of a registered civil engineer in accordance with applicable state and federal regulations and as required in 27 CCR, Section is 20310. 5.2.1 Lower Base Grades In Waste Management Units The base grading plans for Forward Landfill state that wastes may not be discharged below an elevation of 7 feet amsl. WDR Order No. 5-2003-0049 (in effect at that time) allowed lower base grades in the future WMUs to 7 feet amsl so that the former Austin Road Unit were consistent with the original Forward Unit base grades, as shown on Drawing 4. Current WDRs require a minimum 5 -foot separation between wastes or leachate and the highest anticipated elevation of underlying groundwater, including the capillary fringe. Current groundwater elevations fluctuate seasonally but range from approximately -14 to -30 feet below msl. The depth of groundwater fluctuates seasonally as much as 10 feet. According to the San Joaquin County Flood Control District, the historic high groundwater elevation is approximately 10 feet below msl. If the historic high were to occur, a minimum five-foot waste to groundwater separation would be maintained. Given the effectiveness of the base lining system and the minimum separation between the base of the WMU and groundwater, the lowered base grades exceed the technical and regulatory objectives for groundwater and waste separation. Forward Landfill SWT Engineering Joint Technical Document - April 2014 z:\projects\allied waste\forward\five year permit rvw 2013\jtd-5 yr pr 2013\text\sec 5_final.doc