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LCRS Design - Area 213 Foothill Sanitary Landfill TABLE 3 - FOOTHILL SANITARY LANDFILL 2017 LEACHATE DATA: AREA 2A MONTH GALLONS COLLECTED PER MONTH' FLOW RATE (GPD)' FLOW RATE (ft3/day) FLOW RATE (ft3/day/ac) Dec 1,049,710 33,765 4514 309 Average 784,271 25,723 3,439 236 Max 1,512,510 50,417 6740 462 Area of Module 2A: 14.6 acres Information provided by San Joaquin Public Works Department Solid Waste Division From HELP analysis, peak leachate production is estimated to be 1,235 ft3 per acre per day 1 County supplied information 2January was not included in the average calculation as it appears to be anomalous Based on the HELP modeling described above, the predicted peak daily lateral drainage for the active cell condition is 0.34 inches, which converts to approximately 9,240 gallons per acre per day. From the information presented in Table 3, the maximum daily collected leachate was 3,460 gallons per acre per day, which means the GDN can handle 2.7 times the peak 2017 value. Thus, it can be concluded that using the Area 2A peak daily lateral drainage from the HELP model predictions described above is reasonable and conservative relative to the leachate volumes anticipated at the site. 5.0 ALTERNATIVE DRAINAGE LAYER DESIGN 5.1 Transmissivity Title 27, Section 20340(b) requires LCRS systems to handle twice the anticipated maximum daily leachate flow (i.e. factor of safety > 2). To satisfy this requirement, the design transmissivity requirement of the GDN was evaluated using general GDN analysis methods described in the GSE Drainage Design Manual (2007). The factor of safety against failure of the drainage layer was calculated by multiplying the required transmissivity (E)req) by published reduction factors for clogging (chemical and biological) and material creep (compression due to loading), and also by a design factor of safety. Multiplication by the reduction factors and design factor of safety results in the design transmissivity (Odes). Odes was calculated as a function of the peak daily impingement rate (from HELP analyses), the maximum drainage length to LCRS pipe, hydraulic conductivity, and slope of the drainage layer. Transmissivity calculation sheets are included as Attachment 2 to this report. The minimum design factor of safety used in the GDN capacity calculations was 2.0. The specified transmissivity (Odes) of the GDN includes a design factor of safety of 2.0, and results in a transmissivity of 7.1x10-4 m2/s at a vertical stress of 1,000 psf and 2.9x10-4 M2/s at a vertical stress of 11,000 psf. The predicted maximum head of leachate on the liner system Project No. ALI17.1254 1 LCRS Design May 2018