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Above the water-bearing zone, the soil layers are moderately to well-cemented layers of sandstone and siltstone with claystone and conglomerates. This soil is mostly moderately slow in permeability with sporadic sandy layers that are well drained. Construction Module"I" is an unlined module covering approximately 80 acres. Module 1 is provided with composite liner conforming to RCRA Subtitle D and CCR Title 27 as follows (from top to bottom): • 2-foot-thick soil operations layer • 8 oz/synthetic nonwoven geotextile separator/filter • Drainage layer: — Base: 0.75-foot-thick gravel drainage layer with leachate collection troughs with 4-inch-diameter piping — Side slopes: geocomposite drain layer with nonwoven geotextile separator/filter • 60-mil HDPE geomembrane • Geosynthetic clay liner(GCL) on prepared surface • 1-foot thick prepared subgrade(base only). Module 1was constructed in two phases. The first phase of approximately 34 acres was completed in 2003. The second phase of approximately six acres was completed in 2006. COMPLIANCE HISTORY SUMMARY Prior to March 2000,the landfill was found not to impact groundwater. From March 2000 to October 2001, volatile organic compounds (VOCs)were detected at a single groundwater monitoring well,MW-3. These detections have been ascribed to ponding on refuse along a road immediately adjacent to that monitoring well during the winters of 1995/1996, 1996/1997, and 1997/1998. Impact to groundwater at other wells was not indicated. In the spring of 1998, covering of the refuse and grading the area corrected the ponding. However,penetration of water into the refuse below the ponding area apparently caused an increase in landfill gas (LFG)production in the years after ponding was corrected, sufficient to impact the groundwater. Correction of the ponding has since allowed the LFG production to dissipate, and groundwater contamination has not been confirmed in MW-3 since October 2002 (over eight years). In February 2002, water samples from MW-3 indicated that impact to groundwater had ceased. Except for"false positive" detections due to laboratory contamination, impact to groundwater has not been indicated at this well since that time. Contamination has not been confirmed at other groundwater monitoring wells at any time. Foothill Sanitary Landfill 2 Department of Public Works/Solid Waste 1�'Semester 2010 Groundwater Monitoring County of San Joaquin—July 21,2010