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Section 4.0 <br /> Geologic and Subsurface !Conditions. k <br /> The Site is located in the Sacramento Valley subregion of the Central Valley, about-.100 <br /> feet north of the Calaveras River. The Central Valley is a northwest trending <br /> P <br /> sediment infilled asymmetric structural trough. Sediments deposited within the <br /> g <br /> Central Valley range in age from Jurassic to Holocene, and include both marine.and <br /> continental rocks (Page,1989). Based on Page (1989), the Site is-underlain by <br /> Holocene flood-basin deposits that formed by floodwaters entering lowland areas and <br /> depositing fine silt and clay and some fine sand. This unit, shown generically as <br /> alluvium (Qal) on the boring logs,is reported to be up to 160 feet thick and commonly <br /> grades into river deposits composed of sand, gravel, and silt. The nearest identified <br /> active faults are the Marsh Creek-Greenville and Calaveras faults located to the west <br /> approximately 25 and 40 miles, respectively. <br /> US, <br /> The site surface is relatively level at an elevation of approximately 86 feet. It is paved <br /> with an approximately 4-inch-thick layer of asphalt. Beneath the asphalt, our borings <br /> encountered 10 to 25 feet of fill overlying alluvium. The fill consists of wet,very soft <br /> to soft clay and sandy clay. The alluvium consists'of 20 to 25 feet of soft clay <br /> overlying 10 to 15 feet of loose to medium dense sand and gravel overlying stiff to <br /> very stiff clay. <br /> M <br /> Groundwater was measured at 10.5 feet bgs (Elevation.75.5 feet) in PZ-1 on <br /> April 17,2001. <br /> t <br /> R � <br /> I <br />{E <br /> I <br /> 4 <br /> I - <br /> CDM Camp Dresser&McKee Inc. 4-1 <br /> Q:5250Qi29248-GE6T4-RepartlB�kside Pump Sta[ion,doc <br /> y <br /> y k <br />