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WASTE DISCHARGE REQUIREMENTS ORDER R5-2015-0058-01 -25- SAN JOAQUIN COUNTY DEPARTMENT OF PUBLIC WORKS FOOTHILL SANITARY LANDFILL, INC. FOOTHILL LANDFILL SAN JOAQUIN COUNTY Data Source Leachate Head Peak Flow Rate Inches Gal/min Blanket Layer LCRS Piping/Trenches Base Liner Gravel Geonet Lateral Header Model1,2 1 71 18.4 76 148 Regulatory Standard <123 142 374 1524 2964 Design 9 568 295 512 512 1. Based on anticipated or “worst case” peak conditions (e.g., high precipitation, infiltration and runoff during initial waste filling operations) using HELP) Model, Version 3.07. 2. The maximum daily leachate flow calculated using the HELP model was 9,231 gal/acre/day corresponding to 133,826 gal/day over the 14.5 acre module area. 3. Based on 30 cm maximum head authorized for MSW landfill under Subtitle D regulations. See Standard Construction Specification F.2, SPRR. 4. Twice anticipated peak daily flow rate derived from HELP model (expressed in gpm) per Title 27, Section 20340(b). 106. M-2A’s LCRS sump will be constructed in the southeast corner of the M-2A area and will be designed and operated similar to M-1’s LCRS sump. The sump pump will be sized to handle calculated maximum daily and annual average leachate flow rates to the sump (93 gpm and 5 gpm, respectively). A separate LCRS sump may be constructed for the M-2B area. 107. The Discharger plans to construct future modules consistent with existing approvals for Modules 1 and 2, or as separately proposed and approved for a new module. Specific designs and construction plans will be submitted for approval as each module is proposed for development. Construction Specifications D.1 through D.4 of these WDRs require that new LF-2 modules be constructed consistent with the EAD approved under previous WDRs and Title 27 containment requirements applicable to sideslope development over an existing, unlined MSW landfill (i.e., non-composite compacted clay liner or equivalent). Construction Specification D.12 further allows for the Executive Officer to approve less than significant changes to these designs, but requires Board approval of substantive changes. 108. Liners for new Class II WMUs (landfills and surface impoundments) must be designed and constructed to contain fluids (e.g., leachate, waste, and landfill gas (LFG) condensate) to prevent the migration of waste to adjacent geologic materials, groundwater, and surface water (see Title 27, §§ 20310, subd. (a), and 20330, subd. (a)). 109. Title 27 section 20310, Table 4.1, specifies the minimum construction standards for a double lined Class II surface impoundment consisting of: a. A double or single layer clay liner with a hydraulic conductivity of 1 x 10-6 cm/sec or less.