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1 <br /> 16 2.6 Topography, Geology, Hydrology <br /> The site is situated on level terrain. The soils at the property have been mapped by the <br /> U.S D A. Soil Conservation Service as Stockton clay (adobe) Stockton clay is a fine-textured, <br /> dark gray to black clay, deposited by quiescent or slow moving water. The parent material was <br />' of mixed origin, but primarily igneous rock. According to the survey some in-place <br /> development of this soil has occurred also. The development is a tight clay subsoil and is the <br /> result of transport and re-deposition of very fine particles from the top of the soil profile to the <br /> subsoil, resulting in a high colloidal clay content and impervious structure in the subsoil. <br /> 1 <br /> Deeper lithology and site geology is related to the surface soils. The site is mapped by the U.S. <br /> 1 Geological Survey as "basin deposits." Basin deposits have Iithologic profiles dominated by <br /> fine-textured materials. However, intercalating layers of coarser textured materials are common <br /> and usually capable of freely releasing water. Municipal water wells drilled in the general area <br /> penetrate through alternating clays and sands to a depth of 250 feet or more before intentionally <br /> extracting water. <br /> The closest surface water to the site is Duck Creek, approximately 115 of a mile to the north. <br /> Mormon Slough is approximately 1.5 miles north of this site. The piezometric level of <br /> groundwater has been reported to be between 70 and SO feet below the surface at the site (San <br />' Joaquin County Flood Control and Water Conservation District, 1992 data). Municipal wells <br /> seal off the first 250 feet because the upper zones of saturation do not meet quality standards or <br /> do not provide sufficient quantity to be developed (Bulletin 146, California Department of Water <br /> Resources, 1967). Therefore, it is highly unlikely the fuel components at this site have affected <br /> or will affect drinking water supplies <br /> IRegional groundwater flow is expected to be in the north-northeastern direction toward a <br /> groundwater pumping depression Iocated northeast of Stockton (San Joaquin County Flood <br /> Control and Water Conservation District, Spring 1992). <br /> PAR-0593 FNL 3 <br />