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' VVZ1 INC <br /> ' identified (Exhibit 3) The actual locations may be modified based on encountered <br /> '• conditions, results from the soil borings, and soil gas analytical results obtained from the <br /> onsite mobile laboratory during the soil gas survey <br /> ' The soil as sampling depth will be determined from the lithologic and depth to <br /> 9 P 9 P g P <br /> ' groundwater data gathered from the onsite soil borings It is anticipated the initial soil gas <br /> sample will be collected at a depth of 10 feet below ground surface Additional soil gas <br /> ' sample depths will be determined using the following criteria 1) one sample obtained <br /> every ten feet of vertical section penetrated, 2) one sample immediately above any clay <br /> ' or silt layer of three feet or greater in thickness, 3) sample within identified fine grained <br /> lithologic units as well as coarse grained lithologic units, and 4) one sample approximately <br /> four feet above the first encountered groundwater as determined from the soil borings <br /> ' The soil gas sampling protocol is contained in Appendix Ili Two methods will be used to <br /> collect soil gas samples from the subsurface These are 1) sampling directly through the <br /> probe rods using an expendable or retractable drive point and, 2) sampling through small <br /> diameter tubing run down the probe rods (Post Run Tubing system (PRT)) and connected <br /> ' to the probe tip in conjunction with a retractable or expendable drive point <br /> Where potential cross-contamination is present from VOC-contaminated soil, one sample <br /> per boring will be obtained using the first method Probe rods will be advanced to the <br /> selected depth, the probe rod will be pulled up to expose the sampling interval and the soil <br /> ' gas sampling will be initiated Once the sample is collected, the assembly will be <br /> removed The geoprobe will be moved to an adjacent location, one to two feet away, to <br /> ' collect the next soil gas sample at a deeper sampling interval This procedure will be <br /> continued until four or five samples are collected in an area to characterize soil gas in the <br /> ' vadose zone <br /> 12270020 025 6 <br />