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A...:� n � 'Xtn. J. Hunter do Associates informally visited the site during the latter part of 1989 and after accepting the job of preparing this report , re-visited the site on :March 14, 1990. The photos used in Figs . 6 and 7 were taken at that time. AREA GEOLOGY AND HYDROGEOLOCY The project lies in an area that is classified in Reference I as a flood basin of the San Joaquin River , having, shallow deposits of Recent to Pleistocene Age, of flood basin, low permeability, clay, silt , sand, gravel and sometimes organic materials . Sand content in the area is estimated to vary from 0 feet to to feet in the upper 50 feet of material (0 to 20 %) . The preparers of this report did not witness either excavation and have seen onlythe material remaining in the spoil pile seen on Figure 7. Thi materials here, disturbed and mixed by the excavating process, appeared to be vellow colored, silly -sand. The materials excavated were described by Richard Thorpe, who supervised all site operations, as tan colored silty sand. No clays and organic materials were found. The upper 2 feet or so were probably sandy fill material covered by asphalt . No groundwater was encountered during excavating at 12 feet in Excavation !# 1 ; however , some water entered the hole at night and disappeared during the day, indicating some sort of tidal effect . Earth tides can be seen in some shallow water areas even when actual ocean tides are not involved. In any event, ground- water appears to be found at just below 12 feet, surface refer- ence. Inasmuch as the port deepwater channel is only about 150 feet north of the first excavation and the NISL elevation is only about plus 10 feet, water should have been encountered. Average groundwater depth as estimated by the San Joaquin County Flood Control District is shown on Figure 8. The 1989 groundwater elevation shown for the project site is either outside or at the very perimeter of map data. Mr. Freggiaro, Port of Stockton, reported that to his knowledge there are no water wells within perhaps a one mile radius of the site. All water used in the Port is piped- in municipal water. Reference d# I shows the site to overly degraded aquifers which had a chloride content of over 300 ppm as far back as 1963. The current pumping depression of -40 feet shown northerly of the project site likely has drawn and will draw degraded water in that direction. -i -_- The ent-i-report-gigs _in--a_-natura' ly_low-area--that -either—had -to-be - - --- --- filled or regraded during port construction. 5