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WASTE DISCHARGE REQUIREMENTS ORDER NO. R5-2010-0016 -12- SAN JOAQUIN COUNTY DEPARTMENT OF PUBLIC WORKS NORTH COUNTY LANDFILL SAN JOAQUIN COUNTY Module 4 48. A 17 April 2001 letter issued by the Board’s Executive Officer to solid waste landfill owners and operators required a liner performance appraisal for any liner system to be constructed after 1 January 2000, regardless of any liner expansion previously authorized in waste discharge requirements. The performance appraisals were required to include a demonstration that liner systems to be constructed will comply with Title 27 performance standards. 49. In response to the Executive Officer’s April 2001 letter, the Discharger submitted a 14 May 2002 performance demonstration report for Module 4 and future modules (Liner Performance Demonstration for Module 4 and Future Modules at the North County Sanitary Landfill, prepared by EMCON/OWT, Inc.), which (after revision in response to Board staff comment) was incorporated into a September 2002 Report of Waste Discharge (RWD). The RWD proposed an EAD to the Title 27 prescriptive standard Subtitle D composite liner for Module 4 and future modules (see Construction Specifications D.1 and D.2). 50. The results of the Module 4 performance demonstration are summarized in the following table: Data Source Leachate Head Leak Rate1 LCRS Flow Rate2 Blanket LCRS Piping Base Liner Gravel Geonet Lateral Header Inches Gal/acre/day Gal/min Title 27 <12 0.81 --- --- 56.6 145.83 Model 2.4 0.0007 7,295 4,660 28.3 72.9 Design --- --- --- --- 120 500 ____________________________ 1. Assumed geomembrane defect rate of one hole (1 cm diameter each) per acre of liner placed based on best industry practice CQA. 2. Based on anticipated or “worst case” peak conditions (e.g., high precipitation, infiltration and runoff during initial waste filling operations) using Hydraulic Evaluation of Landfill Performance (HELP) Model, Version 3 3. Twice anticipated peak daily flow rates derived from HELP model. The performance demonstration showed that the expected leachate head for the proposed design (2.4 inches) was within the maximum allowed under Title 27 for a MSW landfill (12 inches), and that the calculated leakage rate for the proposed design (0.0007 gal/acre/day) was much less than that for a Title 27 prescriptive MSW landfill (0.81 gal/acre/day). The LCRS lateral and header pipe capacities for the proposed design, 120 gal/min and 500 gal/min, respectively, also exceeded