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4.3 Field Investigation <br /> The scope of work for this project includes an underground utility location survey, the <br /> advancement of up to six soil borings using hollow stem auger drilling and sampling equipment, <br /> and trenching. <br /> 4.3.1 Underground Utility Location Survey <br /> i <br /> An underground utility location survey was condu ted to assess the absence or presence of <br /> unreported underground utilities at the site to clear utilities for the boring locations. <br /> The survey used ground-penetrating radar (GPR) aid radio frequency survey equipment. The i <br /> ' approach for the utility survey was to initially conduct a GPR survey to locally investigate <br /> suspect magnetic anomalies. Based on the GPR su ey results, electromagnetic radio frequency <br /> pipe locating equipment was used to investigate possible underground utilities. s <br /> 4.3.2 Drilling and Soil Sampling <br /> r <br /> Up to six soil borings will be advanced using hollow stem auger drilling­ and sampling <br /> equipment. Soil borings will be located in accordance with Caltrans' Task Order <br /> No. 10-987901-MT. Figure 2 shows proposed boring locations. <br /> The borings will be advanced to approximately 3 m ters'(10 feet).BGS. Discreet soil samples <br /> will be collected at 1.5-meters;(5-,feet)#and at 3 m ters (1'0 feet) BGS. Soil samples will be <br /> collected using a split-spoon sampler lined with metal sample tubes. Soil samples will be field <br /> screened using a photo-ionization detector (PID). Drilling and sampling procedures are <br /> presented in Appendix A. <br /> Following sample collection, the borings will be bac filled with bentonite cement grout from the <br /> bottom of the borehole to ground surface. Drill cuttings will be placed into a 208-liter <br /> (55-gallon) United Nations-approved drum. <br /> All drilling and sampling equipment will be washed prior to use. In addition, to minimize <br /> cross-contamination between borings, all appropriate downhole drilling and sampling equipment <br /> will be washed between borings. Decontamination water will be placed into a 208-liter <br /> (55-gallon) United Nations-approved drum. <br /> 1 i :4.3.3 Trenching <br /> In order to determine'if the leachfield lines were rem wed, a trench will'be excavated'in the area <br /> of the former leachfield. The excavation will extend from east to west, perpendicular to the <br /> former locations of the leachfield lines. The depth of the excavation willibe approximately 4 feet,l <br /> -IMICRFP I'CC MMONLI-DP12002IPRAPJ8183161M".2ab.dw <br /> 4-2 <br />