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INTRODUCTION General This first semester 2012 monitoring report for the Harney Lane Sanitary Landfill (HLSL) is prepared in compliance with Waste Discharge Requirements (WDR) Order No. R5-2009-0049, issued by the California Regional Water Quality Control Board, Central Valley Region on April 24, 2009. The HLSL is located in Northern San Joaquin County at 14750 East Harney Lane, approximately 7 miles east of Lodi (Figure 1). The HLSL is a Class III waste management unit on 127 acres, of which 94 acres received refuse fill. Land within 1000 feet of the property is used for agriculture and grazing. The landfill stopped receiving waste in 1991, and was closed according to Title 14 in October 1994. Before closure, the landfill received approximately 125,000 tons of waste annually. The landfill generally received construction debris and refuse (residential, commercial, and agricultural). At closure, the landfill contained approximately seven million cubic yards of refuse. Geology and Hydrogeology The soils underlying the landfill consists of unconsolidated silts, clays, and sands, which are representative of typical of sediments found in the Central Valley. The soils are typically highly impermeable with hydraulic conductivities of approximately 10-6 to 10-8 centimeter/second. Groundwater is first encountered approximately 120 feet below the surface. Groundwater elevations fluctuate approximately 4 feet during the year. The average groundwater elevation is decreasing steadily over time. Construction The landfill is unlined. A final cover was applied over the area on which refuse was placed to close the landfill in accordance with an approved Closure Plan. This cover generally consists of a minimum 2-foot thick foundation layer overlain by a 1-foot thick clay barrier layer and a 1-foot thick vegetative layer. COMPLIANCE HISTORY SUMMARY The landfill was closed in 1994 in accordance with applicable regulations. Volatile organic compounds (VOCs), including Dichlorodifluoromethane (CFC-12), were first detected in groundwater samples collected from MW-2 (the impacted well) during the second quarter of 1991. Detections of CFC-12 became consistent and repeated after the second quarter 1994 monitoring event. Repeated detections of Tetrachloroethene (PCE) appeared after first quarter 1994 and repeated detections of 1, 2-Dichloropropane appeared after first quarter 1996. The County believes that the presence of VOCs in groundwater collected from MW-2 was due to landfill gas. Harney Lane Sanitary Landfill 1 Department of Public Works/Solid Waste 1t Semester 2012 Groundwater Monitoring Report County of San Joaquin—July 31,2012