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most VOCs(eighteen) were reported in SG-T1. The source of the VOCs in the vadose zone is likely the old unlined portion of the landfill. Methane was detected in four soil gas wells this semester. VOCs have been detected in soil gas since monitoring began in October 2003,but VOC impact to groundwater has only been sporadic with diminished detections since February 2002. The sporadic detection of VOCs in groundwater indicates that the presence of VOCs in the soil at these concentrations is not a significant condition at this landfill. Soil Gas Trench Methane continues to be detected in the soil gas trench. Methane content in the gas beneath the liner of Module 1 is presently between 14% and 37%. When Module l liner was first installed in 2003, the gas beneath the liner was found to vary between 0 and 2%. The HDPE liner was extended over Module"I"refuse in the fall of 2006. It is possible that placing a HDPE barrier over Module"I"refuse has trapped landfill gas beneath. GROUNDWATER DIRECTION AND FLOW RATE Groundwater elevations were measured in monitoring wells during the third and fourth quarters. Groundwater was determined to flow towards the southwest(Figures 3 and 4). The calculated average linear groundwater flow velocity in the third quarter was 117.1 feet per year based on a hydraulic gradient of 0.0035 foot per foot. The calculated average linear groundwater flow velocity in the fourth quarter was 121.2 feet per year based on a hydraulic gradient of 0.0036 foot per foot(Appendix G). The hydrographs indicate a general decline of water levels from a high water level mark in 2000 (Appendix G). This appears to be a result of a general regional change water level elevation, probably by over-extraction of groundwater for irrigation. STANDARD OBSERVATIONS Regular site inspections were performed during the second semester of 2009. Monthly standard observations have been summarized(Appendix H). The electronic signatures on the forms certify that all observations were performed and are accurate. RUN-OFFIRUN-ON FACILITIES The Foothill Sanitary Landfill utilizes several methods to control run-on and run-off. The natural topography of the area controls any run-on into the site. Also, the working area is a significant distance from the property boundary, so run-on from surrounding properties is minimal. To control run-off, a perimeter ditch along the north,west and east ends of the unit directs all storm water run-off into a sedimentation basin on the east side of the site. The rest of the run-off from the unit gathers into a sedimentation basin at the southeast corner of Module 1. There were 40 no breeches to any of the run-on/run-off facilities during this monitoring period. Foothill Sanitary Landfill 10 Department of Public Works/Solid Waste 2nd Semester and Annual 2009 Groundwater Monitoring County of San Joaquin—January 31,2010