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' Job No. 4780200 • Ah Page 5 <br /> ' 2.0 SITE DESCRIPTION <br /> ' A Site Location Map showing the subject site and surrounding area is presented <br /> as Figure 1 of this Work Plan. A site plan, showing the location of the former <br /> ' USTs and fuel dispensing units, is included in this report as Figure 2. Figure 3 <br /> shows the three parcels that comprise the site and indicates the two parcels <br /> ' where sampling will be conducted. <br /> ' 2.1 Geology and Hydrology <br /> ' Stockton and the San Joaquin Valley are part of the Great Valley Geologic <br /> ' Province. The subsurface rocks consist of very thick layers of sedimentary <br /> rocks overlaying crystalline base rock. The sediments were formed during the <br /> ' late Mesozoic (135 to 225 million years ago) and Cenozoic (the last 65 million <br /> years) eras as shallow marine deposits. During this time, the entire California <br /> ' Central Valley was an inland sea. In the case of the San Joaquin Valley, the <br /> seas became shallow and brackish, which led to the formulation, of freshwater <br /> ' lakes towards the end of the Cenozoic era. The surface and shallow rocks and <br /> sediments are composed of recent sediments of gravel, sands, and clays, which <br /> ' are derived from the Coast and Sierra Nevada Mountain Ranges (Norris and <br /> Webb, 1976). <br /> ' The soil underlying the property is classified as Stockton adobe clay. Stockton <br /> adobe clay occupies vast areas of Stockton, especially north and south of <br /> Mormon Slough. The slope is 0% to 1 %. <br /> Stockton series soils are alluvial deposits occupying basin positions. They are <br /> ' strongly developed hardpan soils derived from mixed, but predominantly basic, <br /> igneous material. <br /> 1 <br /> 1 <br /> iEC, Inc. December 23, 1992 <br />