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Problem Assessment Report <br /> Underground Fuel Storage Tank <br /> Site Investigation <br /> 1. 0 Introduction <br /> This Problem Assessment Report presents the results of a soil and <br /> shallow groundwater investigation program as recommended in the <br /> ROY F. WESTON, INC. (WESTON) July 21, 1988 Preliminary Report for <br /> the J.R. Simplot Company site in Lathrop, California (Figure 1) . <br /> The site activities included the installation and sampling of <br /> three shallow groundwater monitoring wells and the gathering and <br /> analysis of soil samples from six locations. All of these <br /> activities occurred in the area of the J.R. Simplot Company <br /> (Simplot) Plant from which two underground fuel storage tanks <br /> were removed (Figure 2) . All of the work described within this <br /> report was conducted under the supervision of a California <br /> Registered Geologist. <br /> 2 . 0 Background <br /> During the removal of two 10, 000 gallon fuel storage tanks at the <br /> Simplot site, soil contamination was discovered within the <br /> excavation. Analysis of soil samples from the excavation indi- <br /> cated the presence of hydrocarbons. Testing and observation of <br /> the two tanks showed that the diesel tank was corroded and showed <br /> signs of leakage through the seams while the gasoline tank was <br /> undamaged and did not leak. <br /> Benzene, Toluene, Xylene & Ethyl-Benzene (BXT&E) compound levels <br /> detected were noticeably higher in the sample collected from <br /> beneath the gasoline storage tank than those observed from the <br /> sample collected from beneath the diesel storage tank. These <br /> results indicate leakage of diesel from the removed diesel tank <br /> and leakage of gasoline from a previous gasoline tank removed in <br /> 1982 . These concentrations detected are listed in Table 1. <br /> TABLE 1 <br /> TANK BOTTOM SOIL SAMPLES <br /> ANALYTICAL RESULTS <br /> ANALYTES AND CONCENTRATIONS mg/kg <br /> Ethyl <br /> j Soil Samples TPH Benzene Toluene Benzene Xylene <br /> Gasoline Storage <br /> Tank (GST - 5) 910 90. 7 369 130 598 <br /> Diesel Storage <br /> Tank (DST - 3) 1000 4 . 6 27 19 79 <br />