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1 been approved by San Joaquin County. The purpose of the work was <br /> to determine "clean zonelewithin hydrocarbon current oooccurrence <br /> anon an to <br /> explore the extent of petro <br /> Appendix C <br />' <br /> The locations of the slots are illustrated in Figure -3, el d feet Soil samples were collected from depths of approximately <br /> below the grade (2 feet below the bottom of the excavation) and 32 to 35 <br /> feet below grade (17 to 20 feet TPIl3o below the <br /> m d the <br /> as well as <br /> samples were analyzed fo <br /> BTEX. Most of the samples collected had diesel concentrations in the <br /> two to ten mg/kg range. The data from this investigation is <br /> summarized in Table 1-2. In general, contaminated soil encountered <br /> 1 during this investigation appeared to be largely confined to the <br /> northeast sector of the excavation (slot 6) at a depth of 33 feet below <br /> grade Some contanunated soil also was detected at a depth of 17 feet <br />' below grade in slot 2 The extent of contamination around slot 2 <br /> appeared to be relatively limited. The absence of gasoline detections, <br /> low diesel detections, and low detections of benzene, toluene, and <br />' xylenes suggest that little contaminated soil remains on the west, <br /> north, and southeast sidesf the to foot depths. <br /> (sample locations S3, S5, <br /> and S1 respectively) at 1 <br /> The results of this investigation are contained in the letter report <br /> submitted by ERM-West �Mr rDeP�slis of conta�nedelveny in AppendixlC to <br /> yers <br /> on October 15, 1990 <br /> this report. <br /> Ge&ogic Setting <br /> The following sections briefly address soil and groundwater <br /> characteristics at the facility <br /> Ground surface elevation at the site is approximately 15 feet above <br /> mean sea level (MSL) Information supplied by the City of Stockton <br /> Public Works Division reported the elevation of the first unconfined <br /> groundwater in the spring of 1990 at 20 feet below MSL This <br />' unconfined groundwater was not encountered during drilling at the <br /> site It is likely that this unconfined groundwater was present at <br /> shallow depths until recent years. Irrigation districts in the area <br />' and the California Department of Water Resources (DWR) have <br /> documented reduction in unconfined groundwater levels of several <br />' feet per year during the 1 years. <br /> During drilling at the site, first <br /> grade. Water lewas velsred at quicklyepose to <br /> th of <br /> between 43 and 48 feet b gr <br />' 1-4 <br />