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WASTE DISCHARGE REQUIREMENTS ORDER NO. R5-2014-0006 -18- <br />FORWARD INC. AND REPUBLIC SERVICES INC. <br />FORWARD CLASS II LANDFILL <br />SAN JOAQUIN COUNTY <br /> <br /> <br />72. The Discharger proposes to install an intermediate liner where new landfill modules/cells are <br />constructed over the existing Class III waste disposal area. The interface liner consists of, in <br />ascending order: one-foot of existing soil cover; one-foot of additional foundation soil; 24-inch <br />low permeability soil (minimum permeability of 1 X 10-7 cm/sec) or GCL liner; 60-mil HDPE <br />geomembrane; geocomposite drainage layer; and one-foot protective cover soil layer. <br />73. The Discharger proposes the following construction quality assurance protocols for liner <br />construction: <br />a. Monitor placement of drainage layer gravel with a dedicated CQA technician; <br />b. a liner leak test over the entire base liner to be performed after installation of the <br />gravel drainage layer and the operations layer; and <br />c. during placement of the first layer of waste in a new unit, site personnel will monitor <br />waste placement and will exclude materials that could threaten the liner. <br />74. The May 2002 (subsequently revised in 2002, 2003, 2007 and 2008) Joint Technical <br />Document includes a stability analysis for the landfill and liner system pursuant to Title 27, <br />section 21750(f)(5). The Discharger based the seismic slope stability analysis on two <br />potential earthquake events, a Maximum Creditable Earthquake (MCE) of M 7.9 on the San <br />Andreas Fault at distance 70 Miles and an MCE of M 6.7 on the Great Valley Fault at <br />distance 21 miles. The slope stability analysis was completed using the program SLOPE/W. <br />The gross stability of the landfill and liner was assessed using the maximum slope height and <br />slope gradient. The final static factor of safety of 1.5 can be obtained for the proposed final <br />cover configuration and no significant seismic-induced permanent displacement is <br />anticipated for the proposed cover design for the design earthquakes. Discharger’s stability <br />analysis includes components to demonstrate the integrity of the landfill foundation, final <br />slopes, and containment systems under both static and dynamic conditions throughout the <br />landfill’s life including the closure period and post-closure maintenance period. The stability <br />analysis demonstrates that the structural components will withstand the forces of the MCE <br />without failure of the containment systems or environmental controls. <br />75. The Discharger proposes to construct new Class II surface impoundments as needed to <br />contain and evaporate leachate from solid waste management units. An engineered <br />alternative to the prescriptive liner requirements of Title 27 is proposed for the Class II <br />Surface Impoundments. The engineered alternative consists of from the top down: <br />a. A primary 60-mil-thick High Density Polyethylene (HDPE) geomembrane; <br />b. a geonet drainage layer, as a Leachate Collection and Removal System (LCRS); <br />c. a secondary 60-mil-thick HDPE geomembrane; and <br />d. a GCL in place of the compacted clay liner. <br /> <br />76. This Order approves the Discharger’s proposed liner system for future modules as described <br />in Finding 6 and requires that the Discharger submit design plans and construction quality