CORRESPONDENCE_2003-2004 - Laserfiche WebLink

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0 10 Development of the Landfill includes placement of additional refuse over Module "I" footprint up to the final design grades. Reaching the design final grades is made possible by the extension of the landfill footprint, such as by the construction of Module 1. However; because Module "I" is unlined, the County plans to place an interface barrier between the refuse now in Module "I" and the refuse placed over Module "I" made possible by the construction of Module 1. This barrier will direct leachate that may be produced in the new refuse placed over Module "I" into the leachate collection system of Module 1. With respect to this barrier, our approach is to propose performance standards for the barrier and then discuss possible barrier configurations that could meet the performance standards. The proposed interface barrier between the WMUs will consist of a soil foundation layer, a low permeability layer, a leachate drainage layer, and a soil operations layer. The soil foundation layer will be placed directly over the existing Module I waste slope in order to provide a working layer and acceptable subgrade for the overlying low permeability layer. A reinforcing layer may be included within the soil foundation layer in order to help bridge any underlying differential settlement within the existing Module I waste. The proposed interface barrier will direct leachate into Module 1. Refuse from Module 1 will be placed above the interface lining system in accordance with the Waste Discharge Requirements, including placement of a two -foot layer of "packer trash" over the operations layer, to protect the interface barrier from puncture or damage from equipment operations in the refuse fill. 2.1. STABILITY ANALYSES Because the inclusion of an interface barrier on the south slope of Module I could impact the slope stability of the refuse placed in Module 1, a stability analysis was performed to evaluate the potentially low interface shear strength between some of the materials that may be suitable as reinforcing, low permeability liner, and leachate drainage layer components. Refuse stability analyses were, therefore, performed to aid in the selection of acceptable materials. Foothill Sanitary Landfill 3 Public Works/Solid Waste Project Design Report County of San Joaquin - August 31, 2004 (Revised November 10, 2004)