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1 <br /> ameO- <br /> 54 <br /> and 57 feet (ft), but the fill mound rises to approximately 62.5 ft in elevation at its highest <br /> point. The fill mound (between 58 and 62.5 ft in elevation) comprises a volume of about <br /> 1,600 cubic yards (yd') of soil (Figure 3). <br /> ' From the early 1900s to the mid-1960s a crude oil storage, pumping,ng, and processing facility <br /> was located at the Former TAOC Tracy Pump Station property. Pipelines connecting the <br /> Former TAOC Tracy Pump Station property to a petroleum storage facility located at the Alden <br /> Park Property may have crossed the southern portion of the Site. Maps presented in previous <br /> 1 investigation reports for the Former TAOC Tracy Pump Station property and the Site also <br /> show pipelines crossing the northern portion of the Site (Dames and Moore, 1989). The crude <br /> ' oil was stored in a concrete-lined reservoir, which is now the site for Alden Park, and was <br /> conveyed by pipelines to a nearby rail yard. <br /> ' 2.1 GEOLOGY AND HYDROGEOLOGY <br /> The Site is located along the western margin of the Central Valley. Quaternary alluvial <br /> deposits shed from the Coast Ranges to the west generate a complex sequence of <br /> ' interbedded clay, silt, sand, and gravel deposits that underlie the Site (Dibblee, 1981). Based <br /> on data collected during previous investigations, and on data collected from monitoring wells <br /> located at the adjacent Former TAOC Tracy Pump Station Property, groundwater at the Site <br /> occurs at approximately 9 to 14 feet below ground surface (bgs), and the horizontal hydraulic <br /> gradient is to the north-northwest. <br /> Based on investigations conducted b Geomatrix Consultants, Inc. Geomatrix in 2001 and <br /> 9 Y (Geomatrix) <br /> 2003, soil encountered at the Site included deposits of clay, silt, and sand to the total depth <br /> drilled. Soil typically consisted of fine-grained deposits (sandy silt [ML] and sandy lean clay <br /> and lean clay with sand [CL]) to a depth of approximately 12 to 16 feet bgs. Beneath the fine <br /> ' grained deposits, interbedded coarse grained deposits (silty sand [SM], clayey sand [SC], and <br /> poorly graded sand with silt[SP-SM]) and fine-grained deposits (sandy silt[ML] and sandy <br /> lean clay and lean clay with sand [CL]) were encountered to the total depth drilled. <br /> 2.2 SUMMARY OF ENVIRONMENTAL INVESTIGATIONS <br /> 1 Soil samples from the Site have been collected during multiple phases of investigation by <br /> various consultants and have been summarized in various reports (Geomatrix, 2001 and 2004; <br /> Table 1). In August 1996, Geomatrix advanced two soil borings (SB-1 and SB-2) to assess soil <br /> in the vicinity of two former pipelines near the southern portion of the property. Samples from <br /> the borings were analyzed for benzene, toluene, ethylbenzene, total xylenes (BTEX) and <br /> polycyclic aromatic hydrocarbons (PAHs; Figure 4). In May 2001, Geomatrix advanced 14 soil <br /> borings across the Site (Figure 4) and collected soil samples that were analyzed for total <br /> petroleum hydrocarbon quantified as crude oil (TPHc), BTEX, and PAHs. The two <br /> 1 AMEC Geomatrix, Inc. <br /> I:\Doc_Safe\6000s\6628.001\3000 REPORTS\Excavation Work Plan-8.12.08\1 Text,cover and slips\Text.doc 2 <br /> 1 <br />