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March 20, 1992 ARCA . ARCO Station No 6100, Tracy, California Selected soil samples collected from the borings were submitted to Sequoia Analytical Laboratory in Sacramento, California (Hazardous Waste Testing Certificate No 1624), for analysis of TPHg and benzene, toluene, ethylbenzene, and total xylene isomers (BTEX) using Environmental Protection Agency (EPA) Methods 5030 and 8020, respectively Samples 5-40-B17 and 5-65-1317 were analyzed for total lead using EPA Method 7241 One composite sample was analyzed for organic lead using the California LUFT Method for disposal of the drill cuttings Analytical results of the soil samples are shown on Table 2 Analytical results of soil samples collected from borings B-7 through B-11, B-14 and B-17 indicated gasoline hydrocarbons are present in soil to a maximum depth of approximately 70 feet bgs (B-9) Dependent upon location within the site, residual hydrocarbons in soil exist at widely varying depths and concentrations With the exception of B-1 and B-7, in the vicinity of the former tank cavity (B-2, B-3, B-4, B-5, and B-6) detectable TPHg in soil is typically limited to a vertical depth of approximately 20 feet bgs with concentrations less than 1,000 ppm (maximum TPHg = 810 ppm in B-4 at 20 feet bgs) Maximum TPHg detected in B-1 and B-7 was 1,900 ppm and 9,500 ppm at depths of 30 and 20 feet bgs, respectively The maximum benzene concentration in these borings was 22 ppm in B-7 at 20 feet bgs In the vicinity of the dispenser islands (B-8, B-9, B-10, B-11, B-14 and B-17) detectable TPHg exists at depths that range from 10 - 70 feet bgs The majority of TPHg detected in these borings exists between the depths of 30 - 50 feet bgs at concentrations that range from 1,400 to 28,000 ppm (B-9 at 25 feet bgs and B-8 at 30 feet bgs, respectively) The terminal depth of boring B-8 (located beneath the canopy) was limited by the inability to drill beyond the 46 foot depth due to the need to use a small drill rig beneath the canopy The vertical extent of TPHg in the vicinity of B-8 is estimated to be between 50 and 70 feet bgs based upon the analytical data obtained from borings B-9 and B-14 The maximum benzene concentration within this portion of the site was measured in B-8 at 120 ppm TPHg was not detected in samples collected from borings B-13, B-15, B-16, B-18 and B-19, these borings establish the lateral maximum limits of TPHg in soil in the north, east and southwest directions from the tank and dispenser areas The analytical results indicated that total lead was not detected in sample 5-40-1317, and 5 6 ppm of total lead was detected in sample 5-65-1317 Organic lead was not detected in composite sample S-1014-1A,B,C,D . 0129ccar 30041-23