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I h <br /> I <br /> of investigation was to complete the assessment of the lateral and <br /> vertical extent of vadose zone contamination, and to install <br /> remedial wells. The following sections discuss the procedures that <br /> were used and the results that were obtained. <br /> 3. 0 PROCEDURES <br /> 3. 1 Drilling and Sampling <br /> Seven soil borings were drilled in May 1993 . Five borings were <br /> advanced to a depth of 60 feet, one (B2) was advanced to 35 feet, <br /> and one (B5) was advanced to 70 feet, using a truck-mounted 8-inch <br /> hollow-stem auger rig. The Mobile Drill B-57 rig and three-man crew <br /> were supplied by Woodward Drilling of Rio Vista. <br /> IDiscrete soil samples were collected at five-foot intervals using <br /> a 140-1b hammer to advance a split-spoon sampler loaded with three <br /> 2-inch by 6-inch brass sleeves . The number of blows required to <br /> advance the sampler 18 inches was recorded on the boring log (see <br /> Appendix A) . To avoid cross contamination, the sampling equipment <br /> was washed in a tri-sodium phosphate (TSP) solution and rinsed <br /> twice with water prior to each sampling run. <br /> After removal from the sampler, soil in the middle tube was <br /> extruded into a plastic bag and screened for volatile organic <br /> compounds using a photo-ionization detector (PID; Thermo <br /> Environmental 580A, 10. 0 eV, calibrated to isobutylene) . The <br /> reading was recorded on the boring log, and the soil was described <br /> I in accordance with the Unified Soil Classification System (Appendix <br /> A) . The ends of the lower tube were covered with aluminum sheets, <br /> capped, sealed with tape, and stored on ice pending on-site <br /> Ianalysis by Geochem' s state-certified mobile laboratory. <br /> 3.2 well Completion <br /> I Boring B5 was completed as monitoring well MW-14 according to the <br /> design shown in Figure 3 , and borings B1, B3 , B4 , and B6 were <br /> completed as vapor extraction wells VW-1 through VW-4 according to <br />' the design shown in Figure 4 . Their locations are shown in Figure <br /> 2 . <br /> 3. 3 Well Monitoring and Sampling <br /> A Solinist water meter was used to measure water depth in MW-14 on <br /> 28 May 1993 . After measurement, the well was purged of 8 gallons of <br /> I standing water, using a stainless steel Grundfos submersible pump. <br /> Temperature, pH, and conductivity were measured at two-gallon <br /> intervals (Table 1) . Purge water was stored in a 55-gallon DOT drum <br /> on the site. <br /> A water sample was collected from MW-14 after temperature and other <br /> I 2 <br />