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STAFF ® r REPORT 2 COUNTY OF SAN JOAQUIN AND FOOTHILL SANITARY LANDFILL,INC. SAN JOAQUIN COUNTY WDRs, Finding Numbers 37 and 38 state: 3 7. 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(µ.g/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." WDRs, Prohibition A.7. states, "The discharge shall not cause degradation of the waters of the state by release of waste constituents in soil-pore gas, soil-pore liquid, soil, or other geologic materials outside of the Unit if such waste constituents could migrate to waters of the State; in either the liquid or the gaseous phase, and cause a condition of nuisance, degradation, contamination, or pollution." WDRs, Facility Specifications C.j. states, "Methane and other landfill gases shall be adequately vented, removed from the Unit, or otherwise controlled, as needed, to prevent adverse health effects, nuisance conditions, or the impairment of the beneficial uses of surface water or groundwater due to migration through the unsaturated zone." Furthermore, WDRs, Landfill Closure Requirements H.2. states, "At closure, each landfill unit shall receive a final cover consisting, at a minimum, of a two-foot thick foundation layer which may contain waste materials, overlain by a one-foot thick clay liner, and finally by a one-foot thick vegetative soil layer, or engineered equivalent as approved by the Executive officer." HISTORICAL OVERVIEW Operations: The active life of the facility is estimated to allow disposal until Year 2050 and closed as one complete Unit. Except for the unlined Module "I," all subsequent expansions surrounding this central Unit are required to be lined to contain landfill leachate and LFG. The original plan for LF-2 modules was to overlap each phase onto LF-1 as each module is lined and filled until final closure of the facility in 2050; 46 years from now. Construction of new Module 1 of LF-2 includes an approximately 34 acre lined module immediately south and adjacent to LF-1, which will be completed soon for acceptance of waste in 2004. Even though the original plan for Module 1 was to line up against Module"I", the Report of Waste Discharge supporting the current WDRs did not include this activity. The Discharger stated that there was not enough time to provide a Liner Performance Demonstration in support for overlapping a liner on Module "I" at the time and that a proposal would be submitted at a later date. The original closure plan for the entire facility is to apply Partial Cover over the side-slopes and top of Module "I" as new Units were built around and overlapping onto this unlined portion of the facility. The remaining side-slopes are to be maintained with a compacted 2- foot soil layer and vegetative cover with drainage and erosion controls. It was intended that this