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' Lodi Ready Mix Page 5 <br /> Site Closure Report <br />,16 Project No. 93.1 <br /> May 12, 1995 <br />' The detection limit for benzene, toluene, Y <br /> eth lbenzene and total xylenes is 5.0 <br /> Y <br /> gg/kg(ppb),2.5 mg/kg TPH-G, and 5.0/50 mg/kg for TEPH. <br />' 2.4 Borehole Closure <br />' After successfully collecting the bottom hole soil sample at 42 feet, the soil <br /> boring was closed by installing a granular bentonite plug at the bottom of the <br />' boring, hydrating it with tap water and then pumping a neat cement grout <br /> (augmented with <4% bentonite) to grade with a slurry pump and a tremie <br /> pipe. A concrete cap was emplaced and finished to the existing grade. <br />' 2.5 Disposition of Soil Cutting <br />' Soil cutting generated during the soil boring installation was added to the <br /> existing stockpile on site within the fenced yard. <br /> ' 2.6 Stockpile Soil Sampling- <br /> In order to further characterize the stockpiled soil from the UST excavation <br /> (pile #3), Geological Technics Inc. personnel collected one grab sample from a <br /> random location approximately 18 inches into the soil pile. Laboratory <br /> analyses showed that the sample contained 66 mg/kg of motor oil (just above <br /> detection limits). The chromatogram did not resemble the standard and the <br /> chemist suggests that the sample is weathered diesel (lighter constituents <br /> have been degraded and only the heavier remain). <br /> ' Due to the relatively low levels of degraded petroleum hydrocarbons <br /> contained in the soil sample, Geological Technics Inc. recommends that the <br /> ' soil pile be approved for unregulated disposal. <br /> ' 3.0 RESULTS OF INVESTIGATION <br /> The data collected during this investigation have been summarized in the <br /> ' following sections. <br /> 3.1 Site Geology <br /> The subsurface geology is characterized by sand with interbedded silt Iayers. <br /> ' The sand ranges in grain size from very fine to coarse (modified Wentworth <br /> scale). The sand contains varying amounts of a silt matrix and a hard sandy <br /> silt layer was encountered at 25 feet. This silt layer contained oxidized root <br /> ' casts which suggest that it is not a reducing environment (typical of soils <br /> 1 <br />