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5 <br /> 4 0 SOIL BORING AND SAMPLING <br /> Soil boring and sampling methodology for this phase of work was presented in <br /> Canonie's Work Plan Soil boring and well locations were based on the results of the <br /> soil vapor survey and information obtained during drilling activities <br /> 4 1 Soil Boring and Sampling Methodology <br /> From October 5 through 7, 1992, seven soil borings were advanced to depths of 15 5 <br /> feet to 35 5 feet in the area of the former tanks Each of these soil borings (W-1 <br /> through W-7) were converted to wells four groundwater monitoring/extraction wells <br /> and three vadose zone vapor extraction wells Well locations are shown on Figure 2 <br /> The Work Plan had proposed four 4-inch-diameter wells to 50 feet and screened from <br /> 5 feet to the bottom of the boring, however, during drilling it became apparent that <br /> the vadose zone was separated from the water-bearing zone by a clay layer that could <br /> be acting as an aquitard To assure that cross-contamination between the vadose <br /> zone and water-bearing zone would not occur, separate wells were installed within <br /> Ieach zone <br /> Drilling was performed by Spectrum Exploration Drilling, Inc of Stockton, California <br /> Seven monitoring/extraction wells were drilled with a truck-mounted CME 550 drill rig <br /> using 8- or 10-inch outside diameter (OD) hollow-stem augers Soil samples from <br /> these wells were collected using an 18-inch-long, 2-inch inside diameter (ID) split- <br /> barrel sampler The sampler was driven in advance of the auger by a 140-pound <br /> weight falling 30 inches The number of blows required to drive the sampler 18 <br /> inches was recorded on the Boring Logs for each 6-inch interval Drilling operations <br /> were supervised by a geological engineer who visually described and lithologically <br /> logged the soil samples at the time of recovery in accordance with the Unified Soil <br /> Classification System Boring Logs are presented in Appendix C All augers and <br /> samplers were steam-cleaned before being mobilized to the site, between each boring, <br /> POW 181 6345REPORTStiSITE ASSWANTECAWANTECA RPT IApr 26 931 Canoe teEnvironmental <br />