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CManteca Unified School District <br /> Soil&Groundwater Investigation Report II <br /> .Page: 5 <br /> grade. A discontinuous clay gray green plastic is present in borings B2, B3, and B5 in the <br /> vicinity of the former fuel dispenser. To the east, in the vicinity of the former <br /> underground storage tank the clay is present only in boring B6. Medium grained well <br /> sorted channel deposits are present within the silty sand in borings B1 and B4. The clay <br /> unit in borings B2, B3, and B5 is underlain by a thin silty sand. The sands are underlain <br /> by a massive wet plastic clay in all borings at depths of 20 to 24 feet. An unconsolidated <br /> medium grained sand is present under the clay.at the base of borings B-5 and B-7. <br /> Groundwater was encountered at depths of 15 feet to 20 feet perched on the clay units in <br /> the borings. A conceptual hydrogeologic cross section is shown in Figure 3. <br /> 4.0 CONTAMINANT DISTRIBUTION <br /> Petroleum hydrocarbons were not detected in any of the soil and water samples collected <br /> during the investigation. The absence of .detectable contamination in bore holes <br /> constructed within 5 feet of the previous sampling points suggest that the previously <br /> reported low concentrations of diesel contamination are an artifact possibly the result of <br /> sampling or laboratory error. A conceptual contamination hydrogeologic cross section is <br /> shown in Figure 4. <br /> L <br /> 4.0 CONCLUSIONS& RECOMMENDATIONS <br /> A sample collected from directly under the diesel dispenser during the 1998 underground <br /> tank removal disclosed moderate concentrations of diesel fuel at three feet in depth. <br /> December 2000 soil boring and sampling, conducted in the area of the former tank and <br /> dispenser, detected low to trace levels of diesel fuel in the soil from 8 to 30 feet bgs and <br /> in the groundwater(<1 mg/1)under the concrete slab of the shop building. <br /> Recent sample collection and.analyses in the area around the former diesel tank and <br /> dispenser did not detect any concentration of diesel or diesel constituents in the area <br /> previously sampled. M.J. Kloberdanz & .Associates recommends no further action <br /> Lregarding the former diesel underground fuel tank. A No Further Action Checklist is <br /> attached in Appendix C. <br />