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1 <br /> Preliminary Subsurface Investigation <br /> City of Stockton, former Western Pacific Railroad Property.Stockton,CA <br /> May 27, 1992 <br /> W0601.1D <br /> the time-chloride lines was in the area of the Deep Water Channel and expanded northeasterly, <br /> rather than the southeasterly direction towards the deepest closing contour of the cone of <br /> 1 depression (Figure D-2). Stratigraphic conditions in the area may be influencing this direction <br /> of water movement in part; Figure D-3 shows that greater thicknesses of sand were encountered <br /> in wells in the channel area than towards the southeast (DWR, 1967). The major control on the <br /> intrusion pattern, however, has been agricultural and municipal pumping east of downtown <br /> 1 Stockton. Although most of.the data used to compute the rate of intrusion are from wells <br /> producing from approximately 150 feet below grade or greater, it is believed that the shallower <br /> ' groundwater zone has been impacted even further eastward and at higher levels than the lower <br /> strata (DWR, 1967). <br /> Information obtained from the USGS' database included construction details, water elevations, <br /> and chemical data of water wells in the vicinity of the subject site based on the topographical <br /> township and range coordinates of 1 North and 6 East. Fifty-two wells were found in the USGS <br /> database search. Completed well depths ranged from 12 to 652 feet below grade. Screened <br /> intervals ranged from 10 to 12 feet below grade in the shallowest well and from 233 to 314 feet <br /> below grade in the deepest well. Depth to water measurements were conducted between 1953 <br /> and 1975 and levels ranged from 6 to 120 feet below land surface datum. Samples were <br /> collected between 1969 and 1979 from seven of the wells in the area and were submitted for <br /> chemical analysis. The sample data shows total dissolved solids (TDS) levels as high as 1,770 <br /> ' mg/f and chlorides as high as 1000 mg/f.. Three of the seven wells exceed the 500 ppm <br /> 1 secondary MCL for chlorides. The secondary drinking water standards for iron and manganese <br /> are also exceeded routinely. The chemical analyses are presented in Appendix D, Table D-1 <br /> 1 and the data is included in Appendix D. <br /> 1 <br /> R04 392.SAY 5 <br /> 1 <br />