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J. H. KLEIN FELDER & ASSOCIATES <br /> File : W-2001-1 <br /> January 29 , 1986 <br /> Page 17 <br /> marine rhyolitic ash, clay, sand, and gravel of the Early <br /> ar <br /> Tertiary Valley Springs Formation. Stratigraphically above the <br /> Valley Springs Formation is the Late Tertiary Mehrten Formation, <br /> composed of moderately well indurated andesitic sands and <br /> . sandstones interbedded with conglomerates, tuffaceous siltstones, <br /> and claystone beds. Above the Mehrten Formation is the Plio- <br /> Pleistocene Laguna Formation, composed of stream-laden, poorly- <br /> sorted discontinuous lenses of continental sand and silt , with <br /> lesser amounts of clay and gravel. Above the Laguna Formation <br /> are continental fan and interfan lenticular gravels , sands , <br /> silts, and clays of the Pleistocene Victor Formation and Recent <br /> alluvium. <br /> B . Site Geologic Conditions <br /> The near-surface soils of the site have been classified as <br /> alluvial fan and flood plain deposits of the Mokelumne area. <br /> Information inferred from the boring logs on the site indicate a <br /> very dense sandy silt at an approximate depth of 40 feet beneath <br /> all three borings. Beneath the site in the location of Boring <br /> No. 2 is a thick lens of clay at a depth of approximately 37 feet <br /> up to approximately 24 feet , which may account for the deeper <br /> l occurrence of water in this location. In this same depth range <br /> J the location of Boring No. 3 is a coarse sand, and beneath the <br />