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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 /> 4.3.2.2 Stockton Landscape Station <br /> Up to two soil borings will be advanced using direct-push sampling equipment. Soil borings will <br /> be located in accordance with Caltrans' Task Order 10-OE7900-MZ. Figure 4 shows proposed <br /> boring locations. The borings will be advanced to approximately 7 meters (23 feet) below <br /> ground surface (BGS). Discreet soil samples will be collected at 1.0-meter(3.3-foot) intervals. <br /> Soil samples will be collected using a 5-centimeter(2-inch) diameter sampler lined with a 1.3- <br /> meter(4-foot) long acetate sleeve. Soil samples will be field screened using a photo-ionization <br /> detector(PID). Groundwater samples will be collected from each deep boring using one or more <br /> of the methods described in Section 4.3.3. Drilling and sampling procedures are presented in <br /> Appendix A. <br /> Following sample collection, the borings will be backfilled with bentonite cement grout from the <br /> bottom of the borehole to ground surface. The surface material will be repaired with cold patch <br /> asphalt or concrete where applicable. Drill cuttings will be placed into a 208-liter (55-gallon) <br /> 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 /> 4.3.3 Groundwater Grab Sample Collection <br /> A groundwater grab sample will be collected from each deep boring. The groundwater samples <br /> will be collected from either well casing inserted into each boring or HydroPunch-type <br /> groundwater sampling equipment. The well casing will consist of 2.5-centimeter(1-inch) <br /> diameter, Schedule 40, flush-threaded, 0.05-centimeter(0.020-inch), machine-slotted polyvinyl <br /> chloride (PVC)well screen. The soil borings may be advanced to greater depths depending on <br /> the groundwater conditions. If free product is encountered, product thickness will be verified <br /> using a disposable bailer. Up to three methods may be used for groundwater collection and these <br /> include the following. <br /> • Dedicated Teflon tubing with a single-ball, stainless steel check valve; or <br /> SAC/DP-N.lroticjpllProjectsl8318370841wp&lrsplSwkton&Pan—i wp.doc 4–� <br /> 513102 <br />