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Problem Assessment Report November 20, 1990 <br /> iFire Engine Company No. 2, Stockton, California AGS 38009-2 <br /> Geologic Cross Section B-B' (Plate P-23) shows silt and clay deposits from 55 feet to <br /> approximately 30 feet below grade. The 20-foot-thick sand deposit encountered in borings <br /> 4D B-1 and B-ti(Plate P-22) apparently does not extend west to boring B-7 and grades to a silt <br /> in boring B-4. This sand deposit appears to have a west-east extent of approximately 25 <br /> 0 feet. The cross section indicates clay deposits surround the sand deposit horizontally and <br /> vertically. )nterfingering sand, silt and clay deposits were logged in boring B-2 to the east; <br /> the sand and clay deposits are approximately 4 feet thick. This grading or interfingering <br /> from clay to sand is common in fan deposits and stream deposits of the Modesto Formation <br /> (Helley Harwood, 1985). <br /> ar <br /> Hydrogeology <br /> e During drilling, ground water was encountered at 37;feet below grade in boring B-1. After <br /> the boring was terminated, the ground water level stabilized at 31 feet before grade. During <br /> driIIing in boring B-2,ground water was encountered at 37 feet(approximately 1 foot above <br /> the poorly-graded sand layer), at 35 feet in boring B-3 (approximately 2 feet above the <br /> poorly-graded sand),and at approximately 38 feet in boring B-4 at the contact of a silt and <br /> clay layer. After these borings were terminated, ground water stabilized at approximately <br /> the same depth below grade. <br /> Mr <br /> 15 <br /> App/ied GeoSYWOMS <br />