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WASTE DISCHARGE REQUIREMENTS -6- FORWARD INC.,FORWARD LANDFILL SAN JOAQUIN COUNTY 29. WMU E, the coal ash landfill unit,has a design capacity of 520,000 cubic yards. 30. Soil contaminated with less than hazardous levels of petroleum hydrocarbons will be treated at WMU G, a Class II land treatment unit. Piles of contaminated soil awaiting treatment will also be stored in the area designated for this WMU. The Discharger has demonstrated that the soil contaminated with less than hazardous levels of petroleum hydrocarbons can be transformed to a `nonhazardous solid waste' within the treatment zone. WMU G may be moved to a new location on the facility as existing WMUs are expanded or as new WMUs are built, as shown on Attachment B. 31. The Discharger also uses four Class II waste piles constructed within the area specified for WMU G for the biotreatment of petroleum contaminated soils. These waste piles are designated here as WMUs G92-1, 2, 3 and 4. These double-lined treatment pads afford greater water quality protection against VOC migration than land treatment units without liners. The pads meet the design requirements for Class 11 waste piles with a synthetic outer liner overlain by a blanket LCRS and an upper clay liner. Upper clay liners were used in the design to withstand the repeated operation of heavy equipment in the waste handling and biotreatment process. Water is applied to soils in the waste piles to optimize moisture conditions for biological degradation of organic contaminants. DESIGN OF WASTE MANAGEMENT UNITS Landfills 32. The containment features of existing landfill units are provided in Finding 5. Starting with WMU D- 93 and all future landfill units in WMU D and WMU H,the liner design is proposed to meet Class II landfill standards in Chapter 15. These landfill units will include a composite liner overlain by a blanket LCRS. The composite liner includes at least two feet of compacted soil with a permeability of 10-7 cm/s or less and a geosynthetic liner at least 40 mil in thickness (minimum 60 mil if HDPE). Future WMU D liners which overlie existing landfill units will include either a composite liner as described above or engineered alternative liner designed in compliance with Chapter 15. Impoundments 33. The liner in WMU F is currently a single clay liner that will be removed before leachate reaches the outer one foot of the liner. The design for future liner systems in WMU F will be submitted prior to construction. Waste Piles 34. Four Class II waste piles were constructed in WMU G in 1992 as biotreatment pads for petroleum contaminated soils. Each waste pile is 40 feet wide by 500 feet long. The waste piles include an outer liner of 40 mil PVC overlain by a blanket LCRS and an 18 inch-thick upper clay liner with a permeability of 10-6 cm/s or less. The clay liner is overlain by blanket LCRS and a protective soil operations layer. The liner in each waste pile has a minimum slope of one percent toward a LCRS collection pipe. The waste piles were constructed in pairs so adjacent units share a central leachate