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' a I <br /> NflMICN�-lfANEN <br /> I Mr. Charles Leubner <br /> 6 February 1998 <br /> Page 2 <br /> f <br /> gravel and Class A/B subbase was imported to complete backfilling of the diesel tank excavation <br /> and pipeline trench. <br /> Of the seventeen soil samples collected from the pipeline trench, only one ,sample (P17) <br /> contained diesel hydrocarbons above laboratory reporting limits. The concentration of diesel <br /> hydrocarbons detected in sample P17 was 1,550 mg/Kg. Because the original backfill material <br /> Iremoved from the trench contained diesel hydrocarbons at concentrations less than the 100 <br /> mg/Kg threshold for acceptable use as backfill material, the soil removed from the pipeline <br /> trench was used to backfill the trench. <br /> . Gasoline Tanks <br /> On 3 January 1997, the two gasoline tanks (Tl and T2) were removed and soil' samples were <br /> collected from the base of,the excavation, the sidewalls; and the stockpiled soil. Only one <br /> sample, Sample 635, contained gasoline hydrocarbons above laboratory detection limits. <br /> Composite samples of the stockpiled soil were collected and analyzed for gasoline range <br /> hydrocarbons. Because laboratory analysis showed neither gasoline hydrocarbons nor benzene, <br /> toluene, ethylbenzene, or total xylenes (BTEX) at or above their respective method detection <br /> 1 limits (refer to Table 2), the stockpiled soil along with clean pea gravel and Class A/B subbase <br /> t was used to backfill the excavation. <br /> f <br /> After presenting the results of the underground storage tank excavation to PHS/EHD in the <br /> Helmick and Lerner Inc. report entitled Underground Storage Tank Removal Report- <br /> Transportation Center, Stockton Unified School District dated 27 January 1997, the County <br /> requested a soil investigation to determine the vertical and lateral extent of petroleum <br /> contamination in and around these areas. <br /> SCOPE OF WORK <br /> Task 1 —Conduct Soil Investigation <br /> Three soil borings are proposed at the former site of the underground diesel tank_ (Tank T7) and <br /> two soil borings are proposed at the remote fill trench near Sample PIT Four soil borings are <br /> proposed for the former location of the underground gasoline tank(Tank Tl). Refer to Figures 2 <br /> j <br /> and ,3 for the proposed location of each soil boring. Drilling activities.will be conducted <br /> 1 according to San Joaquin County regulations and permitting requirements. <br /> r <br /> i <br /> I <br />