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Passive soil gas survey results may be useful in indicating the presence or absence of VOC <br /> vapors in shallow subsurface soil gas and may provide a qualitative measure of the relative <br /> abundance of VOC vapors in shallow subsurface soil gas, if the gas is present.The sample <br /> results are not quantitative in that the results are reported in ion count concentrations for each <br /> specific VOC species detected and are not quantified on a mass per unit volume basis. <br /> Furthermore,the sample results are not necessarily indicative of the presence of VOC vapors in <br /> deeper subsurface soil gas or of VOCs dissolved in underlying groundwater. <br /> The shallow passive soil gas survey results suggested the presence of both TCE and PCE in <br /> shallow soil gas throughout the northern portion of the City of Lodi including the LNC site <br /> (NERI, 1996;Henshaw,2001).PCE and TCE were reportedly detected beneath the LNC site. <br /> 4.3 Drive-Point Soil Gas Survey <br /> A shallow(approximately S feet bgs)drive-point soil gas survey was conducted by the DTSC <br /> during 1993 to assess potential TCE sources in the northern portion of the city of Lodi. A total of <br /> 117 shallow drive-point soil gas samples were collected in two rounds throughout the City of <br /> Lodi. Approximately 74 drive-point soil gas samples were distributed throughout the northern <br /> portion of the City of Lodi. During the first round of sampling, the volume of soil gas collected <br /> was not measured,so the results were qualitative only and were reported in nanograms. During <br /> the second round, the volume of soil gas collected was measured,and the results were reported <br /> in picograms/liter (URS, 1994;NERI, 1996).The results of these soil gas surveys reported the <br /> possible presence of 1,1,1-TCA, PCE,and TCE in shallow soil gas beneath the LNC facility, <br /> primarily below the northwest corner of the parking lot area(Area D,Figure 7). Low-level <br /> concentrations of l,l-DCE and I,I-DCA were also reportedly detected in shallow soil gas in this <br /> same area. <br /> M%in\D:Un,ironmonl.I\LN CNM 0 152007.-pd 17 <br /> is <br />