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E Mr. Robert McClellon March 7, 2011 Page 3 11 J`3 --Z3-0 saKd s, leySd , extends to approximately 53 to 75 feet below ground surface. The preliminary design of the expansion cell places the entire landfill cell construction within the upper soil matrix (Project Description for Land Use Application, Forward Landfill, San Joaquin County, CA, Bryan A. Stirrat Associates, February 2008). If LFG were to migrate from the new landfill cell, it would likely follow preferential pathways of permeable soil (such as the sand, sandy silt and silt) within the soil column that expands the total depth of the landfill cell. In accordance with the CCR Title 27 requirements, the LFG monitoring probes will be constructed to the ma�cimu_m depth of refuse• adiacent to subsurface materials most conducive to gas flow; and contain shallow (within 5-10 feet of surface), intermediate (around half the depth of the refuse), and deep (at or near the depth of the waste) monitoring intervals. Therefore, if the monitoring intervals of the LFG probes are constructed within permeable soil layers, the LFG probes can function as intended at any set -back from the waste limit. To confirm that the monitoring intervals of each LFG probe are constructed at appropriate depth intervals, during installation of the LFG probes, the lithology will be logged in accordance with the Unified Soil Classification System. The permeable lithology within the specified monitoring intervals of each LFG probe will be identified and the LFG probe will be constructed accordingly. The soil descriptions will be recorded onto a field log by a geologist working under the supervision of a California Professional Geologist. New Lined Cell Landfill expansion will be performed in accordance with criteria established in California Code of Regulations Title 27 (Title 27) and Title 40 Code of Federal Regulations Parts 257 and 258 (Subtitle D), and will include installation of a composite liner system and leachate collection and recovery system (LCRS). A prescriptive liner system is proposed for the Forward Landfill Southern Expansion. The slope liner systems are designed to consist of prepared subgrade overlain by a geosynthetic clay liner (GCL), a single -sided textured high density polyethylene (HDPE) liner (textured side down), a non -woven geotextile, a protective soil layer, and municipal solid waste (MSW). Two floor liner systems are proposed: one for areas where waste will be more than five (5) feet above the historic high groundwater level (minus two (2) feet elevation), and another where waste will be placed below this elevation. The prescriptive system currently anticipated (above high groundwater) is: a one (1) -foot operations layer, filter geotextile, one (1) foot of granular LCRS, a cushion geotextile (as needed based on granular material properties), double -textured HDPE membrane, and two (2) feet of low permeability soil. For areas where waste will be within five (5) feet of historic high groundwater levels, the liner and LCRS will likely consist of two (2) feet of operations layer, filter geotextile, one (1) foot of granular LCRS, a cushion geotextile (as needed based on granular material properties), double -textured HDPE membrane, two (2) feet of clay, and an underdrain system with some combination of the following: collection trenches (geotextile/gravel/pipe) on the cell floor; blanket underdrain of geocomposite; blanket underdrain of gravel with geotextile filter. In