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i <br /> :x <br /> File No. 070 <br /> 19 Uecemba 1991 <br /> ` Parc 10 <br /> -• during pumping or draining of the aquifer. It is determined from the distanee-drawdown Graph <br /> based on the calculated trans I nissivi ty,the zero drawdown intercept valve and the distance between <br /> the observation well and the pumped well. T'e five, values obtained for the aquifer storage <br /> co:-iCeient based on the pumping test data fos the Rambo Bakery site were 0.066,0.022,0.017, <br /> 0.011 and 0.019. The average valve was calculated as ID.027. <br /> 4.0 CONCLUSIONS <br /> 4.1 Soil Investigation <br /> Our f.eld observations and laboratory analyses indicated that minor occurrences of petroleum <br /> hydrocarbon contamination exists within the soil in vicinity of the removed underground fuel storage <br /> tanks. However, according to our investigation, the majority of the petroleum hydrocarbon <br /> containinated soil was removed following the 1987 tank removal procedures. The few occurrences <br /> of contaminated soil discovered during our groundwater investi;ation appear to be limited remnants <br /> Uf contaminator! soil 'inadvertently left in place following the 1957 soil excavation and remediation <br /> operation. vie. feel that since the majority of the contaminated soil lfac been removed, no further <br /> action cep—erning soil remediation is warranted. <br /> Composite soil samples of the boring and monitoring well cuttings were collected from the onsite <br /> storage drums. The samples were analyzed in a State of California certified analytical laboratory <br /> for the presence of p;;troleum hydrocarbon products. No detectable levels of TYE or AVO's were <br /> present in either of the composite soil samples (DC-1 and DC-2). Therefor., the drummed soil <br /> cuttings can be discarded. We recommend the soil be either utilized as fill materiA on the site"a. <br /> disposed in a landfill. Copies of the laboratory results for soil samples DC-1 and DC-2 are included <br /> in Appendix VIII. <br /> 4.2 Groundwater Investigation <br /> { Our field observations and laboratory analyses indicated that groundwater ,contamination exists <br /> beneath the subject property as a result of rhe past leakage of undergre;nd fuel storage tanks. <br /> Based on our investigation, it appears that the groundwater contamins.:ion extends over an area of <br /> approximately 22,000 square feet (see Figure 10). We feel that a groundwater remediation system, <br /> should be considered for the Rainbo Bakery site. <br /> �,0 POSSIBLE GRVLINDWATF.R RI;MEC?ATI N AI.TERNATIVF <br /> Several alOrnatives exist for remediation of the contaminated groundwater bericath the Rainbo <br /> Bakery in Stockton. The remediation alternatives can bA subdivided into two categories; 'Q in-situ <br /> rglpediatton and 2 roundw ter extraction systems. In-situ remediation involves the treatment of <br /> the contaminated groundwater as it remains in the aquifer. Groundwater extraction systems consist <br /> of extraction of the contaminated groundwater from the aquifer and treatment following its <br /> extraction. Following are brief discussion of the treatment alternatives and their potential <br /> applications to the Raisibo Bakery site. <br /> ANOERSON <br /> s r- CONSULTING <br /> t <br />