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B. Site Soil Conditions Local soil and rock conditions do not require special design features in the soil gas wells. The site materials from the surface to 300 feet in the landfill vicinity consist of alluvial deposits of two formations, the Laguna and Mehrten Formations. The Laguna Formation consists of consolidated gravels, sandstones, and siltstones. The Mehrten Formation consists of sandstone and siltstone, with conglomerate layers, claystone and mudstone. During well installation, sand lens layers will not be blocked. C. Hydrogeologic Conditions Hydrogeolgic conditions at the disposal site do not require special design features in the soil gas wells. Groundwater near the landfill property is continually being recharged by percolation of surface waters, which originate in the Sierra Nevada and adjacent foothills. Depth to groundwater ranges between 204 feet and 270 feet. Groundwater elevation ranges between 46 feet to 61 feet MSL. Groundwater elevations fluctuate less than one foot seasonally. The groundwater gradient is 0.0015 foot per foot to the southwest. D. Locations of Buildings and Structures Relative to the Migration Monitoring Perimeter Adjacent land use and inhabitable structures within 1,000 feet of the disposal site are primarily agriculture and livestock grazing. At present, there are two residential houses located on properties adjacent to the northwestern property corner of FSL (Figure 1). These residential houses will be considered "off-site structures" and will not be monitored for methane concentration. On-site structures within the monitoring perimeter, such as the scale house, maintenance building, manager's residence and other on-site residences within the landfill property limits, will be monitored for methane concentration (Figure 1). Locations of buildings and structures relative to the migration monitoring perimeter do not require special design features in the monitoring wells. E. Man-M.ade Pathways There are no man made pathways for the transmission of landfill gas off-site near FSL F. Nature, Age of Waste and Potential to Generate Landfill Gas (LFG). The nature and age of the refuse placed in the FSL does not prompt special design features for the LFG migration monitoring wells. Wastes disposed to the site are mostly commercial and household waste, construction/demolition waste, and agricultural waste. Foothill Sanitary Landfill 4 County of San Joaquin Landfill Gas Monitoring Plan Department of Public Works June 25,2010 Solid Waste Division