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Leachate from Module 1 drains by gravity to a sump from which it is either returned directly to the refuse over Module 1 (or other lined module) in accordance with the Waste Discharge Requirements issued by the Regional Water Quality Control Board (RWQCB), or stored in a tank prior to being returned to the refuse. The leachate may also be applied to the waste surfaces. There are eight domestic or agricultural wells within a mile of the facility. There is one domestic well within the permitted boundary of the facility and is used for landfill operation and domestic use for the on-site caretaker. Hydrogeology Soil layers consist of moderately to well -cemented layers of sandstone and siltstone with claystone and conglomerates to a depth of about 200 feet. This soil is mostly moderately slow in permeability with sporadic sandy layers that are well drained. The measured hydraulic conductivity of the native soils underlying the Unit ranges between 5 x 10-3 and 1.4 x 10-' centimeters/second. Groundwater is first encountered at an elevation of approximately 50 ft msl, 120 to 150 feet below the ground surface. Groundwater is unconfined or partially confined and fluctuates less than one foot seasonally. Groundwater flows toward the southwest with an average gradient of approximately 0.002 foot per foot. The groundwater in the San Joaquin River Basin is considered suitable or potentially suitable for municipal and domestic water supply, agricultural supply, industrial service supply, and industrial process supply. The current groundwater monitoring system is comprised of five monitoring wells, one upgradient well (MW -4) and two down gradient wells (MW -3 and -5) and two cross -gradient wells (MW -1 and -2R). Environmental Monitoring Foothill Sanitary Landfill had not affected the groundwater prior to March 2000. From March 2000 to October 2001 (approximately 19 months) VOCs were detected at one well, MW -3. Contamination was ascribed to LFG impact, caused by ponding along a road on refuses adjacent to MW -3 from three previous winters. This ponding apparently caused an increase in LFG generation in the refuse beneath the ponding area, which impacted the groundwater. This area was graded prior to the VOC detections, which prevented further ponding. Impacts to groundwater by leachate is not indicated. In June 2003, the Evaluation Monitoring Program was completed and found temporary borings to be free of contaminants. VOC impacts to groundwater have not been seen since October 2001 (approximately seven years). Run-off/Run-on Facilities Corrective Action Financial Assurance Cost Estimate 1 September 30, 2008 Foothill Sanitary Landfill Public Works/Solid Waste Div.