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r <br /> Previous Sampling Results <br /> Constituent Detection Tank No. Tank No. Tank No <br /> ( mg/kg) Limit 1 2 3 <br /> �» ------------------------------------------------------------------- <br /> Benzene 0.2 ND ND ND <br /> Aylene 0. 2 ND 1. 5 5 7 <br /> Toluene 0 2 ND ND ND <br /> Volatile <br /> Hydrocarbons 1.0 ND 52 64 <br /> Ethylene Dibromide 0.02 NA ND ND <br /> Total Extractable <br /> Hydrocarbons 10 ND 130 160 <br /> �a Total Lead -- NA 17 20 <br /> EBF NA = Not analyzed <br /> ND = Not detected <br /> 5 <br /> The sample under the diesel tank (Tank No. 1 ) found no <br /> significant detectable residues of the contents of the tank. <br /> The sample from under the two gasoline tanks found <br /> detectable amounts of total petroleum hydrocarbons and lead. <br /> Of the findings, the lead level was the most significant. <br /> Lead under Tank 2 was reported as 17 mg/kg. Tank 3 soils <br /> were reported to contain 20 mg/kg of lead. <br /> 2. 5 Estimates of liquid quantity and composition leaked: <br /> No estimate of liquid can be made with existing information <br /> The constituents detected in the soil samples are typically <br /> derived from gasoline and or diesel fuel. Detectable soil <br /> contamination appears to be more concentrated near the north <br /> end of the tank pit, however the concentrations are very <br /> low. Therefore, we believe overspillage was the most likely <br /> source. <br /> 2 6 Regional topography, geology, hydrology: <br /> The site is situated on level terrain The soils -.n the <br /> vicinity of the Chevron property have been mapped by the <br /> rr 5.D A. Soil Conservation Service as Stockton clay (adobe) <br /> Stockton clay is a fine-textured, dark gray to black clay, <br /> deposited by quiescent or slow moving water. The parent <br /> material was of mixed origin, but primarily igneous rock. <br /> According to the survey some in-place development of this <br /> soil has occurred also The development is a tight clay <br /> subsoil and is the result of transport and re-deposition of <br /> very fine particles from the top of the soil profile to the <br /> subsoil, resulting in a high colloidal clay content and <br /> impervious structure in the subsoil. <br /> The impermeability causes temporary perched water tables and <br /> 3 <br />