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a3 <br /> Geological Tec/uticsl�re. Page 2 <br /> Groundwater Monitoring Report <br /> Project No. 1030.2 <br /> October 22, 2004 <br /> the USGS Topographic Map reveals that the elevation of this site is approximately 75 feet <br /> above mean sea level (AMSL). <br /> The site is located on the gradually sloped floor of the northern San Joaquin Valley. <br /> The <br /> geologic composition of the area is characterized as fluvial deposits of the San Joaquin - <br /> Sacramento River delta system that overlay continental rocks and deposits derived from <br /> erosion of the Sierra Nevada Mountain Range located approximately 50 miles northeast of <br /> Modesto. <br /> ' The southwest tiltingSierra <br /> Nevada fault block underlies the northern San Joaquin Valley <br /> ' area. Overlying the consolidated rocks are unconsolidated sediments. The lower consolidated <br /> batholithic and metamorphic rocks are poorly transmissive, however the overlying <br /> sedimentary layers are often quite permeable. These unconsolidated layers include <br /> Pliocene/Pleistocene age continental deposits, Pleistocene age lacustrine and marsh deposits, <br /> and Holocene older and younger alluviums and flood-basin deposits. <br /> 1.2 Regional Stratigraphy <br /> The following information comes from the United States Department of Agriculture — Soil <br /> Conservation Service (USDA). Soil Survey of San Joaquin County, California (McElhiney, <br /> M. A., 1992), indicates the area surrounding the site is predominately made up of one general <br /> soil type: <br /> ' e Capay — Stomar— Zacharias: A gentle 0 to 2 percent slope; moderately well drained and <br /> well drained, moderately fine textured, gravelly moderately fine textured, and fine <br /> textured soils that are very deep; in interfan basins and on alluvial fans and stream <br /> ' terraces. <br /> • The USDA Soil Survey of San Joaquin County, California (McElhiney, M. A., 1992), <br /> states the soils beneath and adjacent to ST are categorized as: <br /> to Capay clay: Wet 0 to 2 percent slope; very deep, moderately well drained, nearly <br /> level soil is in interfan basins. It formed in alluvium derived from mixed rock <br /> sources. Typically the surface layer is grayish brown and dark grayish brown clay <br /> about 20 inches thick and the next 60-inches is typically pale brown silty clay <br /> loam and clay loam. Slow permeability, high shrink-swell potential, low strength, <br /> and high water table. <br /> ' 1.3 Site-S ecific H <br /> p ydrogeology <br /> ' - A site map showing the locations of streets, structures, wells; and other site-related details is <br /> attached as Figure 2. <br /> ' 1.3.1 Lithology and Soil Characteristics <br /> The shallow geology of the site is characterized by clay and silt primarily gray in color with <br /> varied degrees of plasticity. A dirty sand layer was encountered throughout the site at <br />