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