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� <br /> A-2 <br /> of the various strata, the "N" value, and pertinent information regarding the method of maintaining and <br /> advancing the borehole was made. <br /> All drilling and sampling equipment was cleaned before drilling each boring using a high-pressure, steam- <br /> cleaning apparatus. The split-spoon sampler was cleaned with phosphate-free soap and rinsed with water <br /> following each sample collection. Soil cuttings generated during drilling operations were placed on and <br /> covered with visquene on site until laboratory results are obtained and proper methods of disposal have <br /> been approved. <br /> 3.0 S01IL SAMPLE SCREENING <br /> After the vapors in the soil samples were allowed to equilibrate with the air in the headspace of the plastic <br /> bags, the organic vapors within the headspace were screened with a PID equipped with a 10.2 eV lamp <br /> calibrated to hexane. The sample bag was opened and the detector probe immediately placed within the <br /> headspace of the bag. The highest observed reading was recorded. This number provides a relative <br /> comparison of the petroleum hydrocarbon concentration with the soil samples but is not quantitative. <br /> Selected soil samples were submitted to a California-certified laboratory for analysis of benzene, toluene, <br /> . ethylbenzene, xylenes (BTEX), and total petroleum hydrocarbons (TPH) as gasoline concentrations. <br /> 4.0 GROUND WATER SAMPLING <br /> Ground water samples were collected with a Hydropunch sampling device. The Hydropunch was pushed <br /> into the upper water table aquifer, then withdrawn to expose an inlet screen. A I-inch diameter stainless <br /> steel bailer was then used to retrieve a water sample. The Hydropunch and bailer were cleaned prior to <br /> each use with a high-pressure steam-cleaning apparatus. <br /> 5.0 VAPOR EXTRACTION WELL INSTALLATION <br /> Confirmation boring CB-4 was completed as soil vapor extraction well VEW-1, a nested well containing <br /> three separate casings screened at various depths. Each casing is 2-inch diameter flush-threaded Schedule <br /> 40 PVC, with 0.020-inch slots in the screened interval. The generalized well construction detail is <br /> illustrated in Figure 3. <br /> LRP38I.SJH <br />