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9 0 <br /> Beck Property,Tracy,CA November 1988 Site Investigation <br /> INVESTIGATION FINDINGS AND CONCLUSIONS <br /> This section of the Site Investigation Report presents the findings and conclusions resulting <br /> from AEMC's implementation of the field, analytical and research activities described in <br /> the previous section. <br /> Field Investigation <br /> Refer to Figure 2 or Appendix 1 for a description of the environmental sampling locations. <br /> Refer to Table 1 and Appendix 3 for the results of laboratory analyses performed on <br /> investigation samples. <br /> Surface Soil Samples <br /> AEMC field observations provided no evidence to suggest the existence of <br /> contamination in the surface soil (0 to 6-inch depth) at either sampling sites. <br /> However, AEMC suspected that low levels of persistent organochlorine pesticides <br /> might be detected in the surface soil due to past agricultural practices common to <br /> the area. <br /> Laboratory analyses detected 37 mg/kg of Total Recoverable Hydrocarbons (EPA <br /> Method 418.1) in the composite sample collected within the perimeter of the <br /> reservoir. No Total Recoverable Hydrocarbons were detected in the composite on <br /> the Tracy School District property immediately north of the Beck site. <br /> Explanation for the presence of this low quantity of hydrocarbons in the reservoir <br /> surface soil composite sample could be laboratory or analytical method detection <br /> error. However, the results suggest that hydrocarbon volatiles/vapors could be <br /> migrating upwards through the soil column, thus the low level of hydrocarbon <br /> contaminants in the surface soils. Upon review of the aerial photograph depicted on <br /> Figure 3, the location of the oil reservoir is clearly depicted through soil <br /> discoloration - possibly the result of minor depletion of organic matter in the surface <br /> soil due to the upwards migration hydrocarbon vapor. <br /> �rou= Page 10 <br />