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INTRODUCTION General On behalf of San Joaquin County(County), Shaw Environmental Inc. (Shaw) has prepared this fourth quarter and annual 2006 monitoring report for the Harney Lane Sanitary Landfill (HLSL) in compliance with Waste Discharge Requirements (WDR) Order No. 96-139. The WDRs were issued by the California Regional Water Quality Control Board, Central Valley Region, on May 3, 1996. 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. 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 residential and commercial refuse, construction debris, and agricultural waste. Geology and Hydrogeology The soils immediately underlying the landfill consists of unconsolidated silts, clays, and sands to a depth of approximately 80 feet. 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 throughout the year. The average groundwater elevation is decreasing steadily over time. Construction The landfill is unlined. To close the landfill, a final cover was applied to the area on which refuse was placed. The final cover consists of a minimum 2-foot foundation layer overlain by a 1-foot thick clay barrier layer and a 1-foot thick vegetative layer. COMPLIANCE HISTORY SUMMARY 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. The County believes that the presence of VOCs in groundwater collected from MW-2 was due to landfill gas influence. A landfill gas collection system was installed in 1996 and has been operated to mitigate groundwater impact and to control off-site migration of landfill gas. Current data shows a continuing decrease in Harney Lane Sanitary Landfill Department of Public Works/Solid Waste 4" Quarter and Annual 2006 Groundwater Monitoring Report County of San Joaquin—January 15,2007 1