ARCHIVED REPORTS_JULY 2014 FINAL RCSI

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WASTE DISCHARGE REQUIREMENTS ORDER NO. R5-2014-0006 -17- FORWARD INC. AND REPUBLIC SERVICES INC. FORWARD CLASS II LANDFILL SAN JOAQUIN COUNTY 67. On 30 May 2002, the Discharger submitted a Joint Technical Document requesting approval of single composite bottom liner that complies with the prescriptive standard liner requirements and an engineered alternative to the prescriptive standard for the side slope liner requirements for all future modules at the facility. Future landfill modules shall have a single composite bottom liner that consists of, in ascending order: a prepared subgrade; a 24-inch thick, low-permeability soil layer (minimum permeability of 1 X 10-7 cm/sec); a 60-mil high density polyethylene (HDPE) geomembrane; a 12-ounce/square yard cushion geotextile (may be omitted if the LCRS gravel is sub-angular to rounded); a 12-inch LCRS gravel drainage layer; an 8-ounce/square yard separator geotextile; and a 12-inch thick protective cover soil operations layer. The components for the engineered alternative side slope liner of the future landfill modules consists of, in ascending order: a prepared subgrade; a Geosynethic Clay Liner (GCL) or a 24-inch thick low permeability soil layer (minimum permeability of the soil 1 X 10-7 cm/sec); a 60-mil HDPE geomembrane; a geocomposite drainage net; and a 12-inch thick protective cover soil operations layer. 68. The Discharger’s engineered alternative demonstration contends that installation of 24- inches of compacted low permeability soil and gravel drainage material on side slopes will be technically difficult and would cost substantially more than the use of GCL and geocomposite drainage net respectively (the alternative design). 69. The Discharger adequately demonstrated that construction of a Subtitle D prescriptive standard liner would be unreasonably and unnecessarily burdensome when compared to the proposed engineered alternative design. The Discharger demonstrated that the proposed engineered alternative is consistent with the performance goals of the prescriptive standard and affords at least equivalent protection against water quality impairment. 70. The approved leachate collection and removal system (LCRS) consists of a 12-inch gravel layer with six-inch high density polyethylene (HDPE) lateral pipe and headers. The drainage layer has a minimum 2% grade towards the leachate collection pipes and minimum 1% grade along the leachate collection pipes. The leachate collection pipes are placed on approximately 200-foot centers. Calculated peak daily leachate generation is 4,073 gallons/acre or approximately 0.0045 cubic feet per second. Daily peak head on the liner system is calculated to be approximately 1.6 inches. Collected leachate is either recirculated to composite-lined landfill units or discharged to one of the onsite Class II impoundments. Recirculated leachate may be discharged by spraying from a tanker truck or by subsurface injection. 71. A pan lysimeters will be installed beneath the LCRS sump in each new landfill cell/module for the purpose of vadose zone monitoring. The proposed design for the pan lysimeters consists of, in ascending order: a prepared subgrade; a 24-inch thick, low-permeability soil layer (minimum permeability of 1 X 10-7 cm/sec) or a GCL liner; a 60-mil HDPE geomembrane; and a gravel filled pan lysimeter with access pipe. Overlying the pan lysimeter is the primary sump which consists of a GCL liner; a 60-mil HDPE geomembrane; a gravel filled LCRS sump with access pipe; an 8-ounce/square yard separator geotextile; and a 12-inch thick protective cover soil operations layer.