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w ,: OWN <br /> F <br /> 171-90 <br /> SEISMIC SETTING <br /> 3 <br /> The closest major faults are the San Andreas, Hayward, and Calaveras faults located <br /> F approximately 63, 47 and 40 miles respectively, from the site vicinity. Manteca has <br /> been classified as part of Seismic zone III by the San Joaquin County uniform Building <br /> Code; 1988 addition (Chapter 23). Seismic risks are moderate in this zone. <br /> i . <br /> aa, <br /> s GROUNDWATER CONDITIONS <br /> ' Groundwater occurs under both confined and unconfined conditions in the San Joaquin <br /> Valley. The degree of confinement varies widely because of the heterogeneity <br /> (variability) of the continental deposits. The body of fresh groundwater in the San <br />_ Joaquin Valley is contained in principally unconsolidated continental deposits of Pliocene <br /> to Holocene Age (0-7 million years old) that extend to depths ranging from less than <br /> t 100 feet to more than 3,500 feet. Along the eastern boundary of the valley at shallow <br /> �.. depths, the base of fresh ground water occurs In more consolidated marine and <br /> i'6 <br /> continental sedimentary rocks of Tertiary Age (2-65 million years old). The depth to <br /> � r <br /> . groundwater at the subject site is approximately i 8 feel below the ground surface base <br /> E ; <br /> on drilling during the site assessment. The groundwater gradient In the vicinity of the <br /> -. site is calculated to be to a north st, ta gradient of approximately 0.005 feeVfoat <br /> (FIcU!1S 3). Artificial and recharg can greatly influence groundwater depth, <br /> i, <br /> especially if the water table is shallow. The verage annual rainfall for the general site <br /> vicinity is 12 to 14 Inches (Hornbeck, 198 <br /> , <br /> 6 <br />