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WASTE DISCHARGE REQUIREMENTSORDER NO. R5-2003-0020 -6- FOR COUNTY OF SAN JOAQUIN FOR CONSTRUCTION, OPERATION, CLOSURE AND EVALUATION MONITORING FOOTHILL SANITARY LANDFILL, MUNICIPAL SANITARY LANDFILL SAN JOAQUIN COUNTY �. above its MDL is sufficient to provide for the earliest possible detection of a release, the detection of two non -naturally occurring waste constituents above the MDL as a trigger is appropriate due to the higher risk of false -positive analytical results and the corresponding increase in sampling and analytical expenses from the use of one non -naturally occurring waste constituent above its MDL as a trigger. 37. The monitoring results indicate that landfill gas (LFG) from the unlined Module "I" at the Foothill Landfill has impacted groundwater. The volatile organic compounds (VOC) have been confirmed in well MW -3 and the VOCs that are most prevalent are Tricholoroethene (TCE) and 1, 1 -Dichloroethene (1,1-DCE). TCE had eleven quantified detections with a maximum concentration of 4.0 micrograms per liter (µg/1) and an average concentration of 0.78 µg/1. 1,1-DCE had six quantified detections with a maximum concentration of 0.32 µg/1 and an average concentration of 0.16 µg/1. 38. Title 27 requires the Discharger submit to the Board an engineering feasibility study for a corrective action program necessary to meet the requirements of §20430. At a minimum, the technologic and economic feasibility study shall contain a detailed description of the corrective action measures that could be taken to achieve background concentrations for all �. Constituents of Concern and the closure of Module "I." 39. On 15 September 2000 the Board adopted Resolution No. 5-00-213 Request For The State Water Resources Control Board To Review The Adequacy Of The Prescriptive Design Requirements For Landfill Waste Containment Systems To Meet The Performance Standards Of Title 27. The State Board responded, in part, that "a single composite liner system continues to be an adequate minimum standard" however, the Board "should require a more stringent design in a case where it determines that the minimum design will not provide adequate protection to a given body of groundwater." 40. In a letter dated 17 April 2001, the Executive Officer notified Owners and Operators of Solid Waste Landfills that "the Board will require a demonstration that any proposed landfill liner system to be constructed after 1 January 2002 will comply with Title 27 performance standards. A thorough evaluation of site-specific factors and cost/benefit analysis of single, double and triple composite liners will likely be necessary." 41. The Discharger provided a single -composite liner system leak performance demonstration. The leakage rate through the proposed liner was calculated from the available head over the liner and assumed quantity of leaks. The maximum available hydraulic head of leachate on the HDPE liner was estimated to be to be 1.7 inches (HELP -3 model), based on the leachate reaching the LCRS system of Module 1 and the removal of the leachate by the LCRS. These