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1.0 INTRODUCTION This report presents the results of subsurface investigations conducted to date to assess hydrocarbon and d1 waste oil contamination on the property located at 1587 French Camp Turnpike in Stockton, California (Figures 1 and 2) . The property is currently vacant but was previously operated as a service station. On July 12, 1989 three underground (u/g) diesel storage tanks and associated piping were removed from the subject property along with one waste oil tank (Figure 2). Two soil 4 samples were recovered from beneath each end of the diesel tanks at depths ranging from 13.0 to 14.5 feet below grade. Four samples were collected beneath the product lines and dispensers at depths of 3.0 to 4.0 feet and one sample was collected beneath the waste oil tank at 12.5 feet. The locations of the eleven soil samples collected during tank and line removal are shown on Figure 2. The laboratory results of these samples are summarized on Tables 1, 2 and 3. The laboratory data sheets and chain-of-custody documentation for these samples are contained in Appendix I. .:., The sample results showed moderate levels of diesel -r hydrocarbon contamination (650 ppm) in soils beneath the west end of the middle diesel fuel tank. There were also elevated levels of d'?sel hydrocarbons (4500 ppm) and low levels of semi volatile organics (2-methylnapthalene 3G ppm and phenanthrene 5.3 ppm) associated with the waste uil tank. In addition, various metals were detected in the waste oil tank sample. Based on these positive leak indicators, the San Joaquin County Public Health Services Department, Environmental Health Division (SJCEHD) required an investigation to assess the extent of contamination. Additional investigations conducted to date have included 1) excavation of hydrocarbon contaminated soils from the diesel tank pit and soil sampling of excavation walls/floor 2) drilling and soil/groundwater sampling of a monitoring well located adjacent to the waste oil tank and 3) drilling and soil sampling of an angle soil boring beneath the building adjacent to the waste oil tank. These investigations were conducted in accordance with WaterWork's proposals dated October 11, 1989 and February 5, 1990 and an addendum dated November 21, 1989 which were submitted to the SJCEHD for prior approval. The proposals were drafted and the investigation conducted in accordance with the Tri Regional Guidelines prepared by the Regional Water Quality Control Board. � y l