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to Recent (present time). The site rests on Flood Basin Deposits which dominate the Delta area <br />of San Joaquin County, the lowest portion of the San Joaquin basin. The sediments are <br />relatively flat -lying, and generally conformable, indicating that deposition historically has been <br />virtually continuous. Sediments in this formation are generally fine-grained with a higher <br />percentage of fine -sand and clays than their depositional equivalents to the east and west (DWR <br />Bulletin No. 146, 1967). <br />Occasional pockets of usable fresh water are found in the Flood Basin Deposits but, generally, <br />the formation contains poor quality water (USGS, 1986). Deeper irrigation wells draw their <br />water from the underlying Laguna Formation. The lithology of the Laguna Formation consists <br />of discontinuous lenses of sand and silt with lesser amounts of clay and gravel. The major water <br />producing area of the Laguna Formation lies between the Delta and the lowest foothills of the <br />Sierra -Nevada Mountain Range to the east (DWR Bulletin No. 146, 1967). The flood basin <br />deposits of the shallow water bearing zone have well developed soil profiles and consequently <br />poor permeability. <br />Based on data from borings, the soils beneath the subject site are comprised primarily of clays <br />and silts with some poorly graded sand from the surface to approximately 45 feet below surface <br />grade, the total depth explored. <br />Regional groundwater depth is reported to be approximately 15 to 20 feet below grade (San <br />Joaquin County Flood Control and Water Conservation District [SJCFCWCD], Spring 1995). <br />When groundwater levels were last measured in June 1996 the depth to water was approximately <br />12.8 feet. The regional groundwater gradient is northeasterly toward a pumping depression <br />~" located northeast of Stockton (Appendix A). Groundwater flow at nearby sites has varied from <br />roughly northeast to southeast. At the nearest known site, located at 1904 W. Charter Way, <br />groundwater flow in March 1996 was to the northeast. <br />groundw\ranuioklosure 2 <br />