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because of the presence of petroleum hydrocarbons. At the time of sampling, a thin layer of free <br /> i product was observed floating on the water in MW-1 (Geological Technics, 1996). <br /> 2.2 Geology. <br /> Vemalis is located in the Central Valley Physiographic Ph siogra hic Province of California. The <br /> valley is about 40 mules wide, bounded by the Coast Ranges to the west and the Sierra Nevada <br /> Range to the east. In the vicinity of Vemalis, unconsolidated Quaternary alluvial and fluvial <br /> sediments are found to a depth of at least 400 feet. Most of these soils were deposited in alluvial <br /> fans associated with rivers draining the Sierra Nevada Range. Coarser materials are associated <br /> with stream channel and natural levee deposits, while finer grained soils are associated with <br /> floodplains and marshes, historically associated with rivers along the axis of the Central Valley <br /> (WHF, 1996). <br /> iSoil borings at the site indicate that, to a depth of 50 feet bgs, soils are <br /> heterogeneous, consisting of relatively thin sand and gravel separated by silt and clay (see also <br /> Section 4.1 this report, Geological Technics, 1996). <br /> 2.3 Hydroloey <br /> Limited shallow groundwater information is available for this site. A monitoring <br /> well (MW-1) with a screened interval of 25 to 40 feet bgs had a groundwater level of 30 feet bgs <br /> in September 1996 (Geological Technics, 1996). In the current investigation, groundwater was <br /> encountered between 29 and 31 feet bgs (Section 4.1). The groundwater gradient and flow <br /> direction at this the site are not currently known. <br /> I� 35275 Welty Road,Vemalis 6 March 1997 I�I <br /> I I <br /> 1 <br /> 3�j1$t <br /> l <br />