Laserfiche WebLink
George's Service <br /> Remedial Action Work Plan <br /> Project No.425.2 <br /> June 30,2011 <br /> The Site is located on the gradually sloped floor of the northern San Joaquin Valley. 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 tilting Siena Nevada fault block underlies the northern San Joaquin Valley <br /> area. Overlying the consolidated rocks are unconsolidated sediments. The lower <br /> consolidated batholithic and metamorphic rocks are poorly transmissive; however the <br /> overlying 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 /> 3.2. 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 /> • Capay—Stomar—Zacharias: A gentle 0 to 2 percent slope; moderately well drained <br /> and well drained, moderately fine textured, gravelly moderately fine textured, and <br /> fine textured soils that are very deep; in interfan basins and on alluvial fans and <br /> stream terraces. <br /> • The USDA Soil Survey of San Joaquin County, California (McElhiney, M. A., 1992), <br /> states the soils beneath and adjacent to the site are categorized as: <br /> o Capay clay: Wet 0 to 2 percent slope; very deep, moderately well drained, <br /> nearly level soil is in interfan basins. It formed in alluvium derived from <br /> mixed rock sources. Typically the surface layer is grayish brown and dark <br /> grayish brown clay about 20 inches thick and the next 60-inches is typically <br /> pale brown silty clay loam and clay loam. Slow permeability, high shrink- <br /> swell potential, low strength, and high water table. <br /> 3.3. Lithology and Soil Characteristics <br /> The following summary discusses the subjective field observations and geology documented <br /> during various investigations based on the interpretations of the field geologist. <br /> • The lithology of the Site is predominantly alternating layers of clay-sand mixtures <br /> and sand-gravel mixtures. <br /> • The lithology between the surface and 20-feet bgs is predominately clays and sands. <br /> • The lithology between 20 and 40-feet bgs is predominately sands and gravels. <br /> • The lithology between 40 and 80-feet bgs is comprised of alternating layers of clay- <br /> sand mixtures and sand-gravel mixtures approximately 2 to 8 feet in thickness. <br /> geologicalTecltatcs6rc. 5 <br /> 4252 RAP.docx <br />