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l r Work Plan— 1,2-DCA Investigation Former American Forest Products Site,Stockton,California April 2,2002 URS Corporation Americas Page 3 2.4 SAMPLING PROCEDURES All field procedures will be overseen by a URS geologist, under the direction of a California Registered t Geologist. Procedures for drilling and groundwater sampling are outlined in the following sections. The on- site geologist will be present at all times during drilling in order to observe the drilling subcontractor, and to collect and manage samples. During drilling, each borehole will be advanced using a direct-push, van-mounted rig equipped with 1.5-inch diameter steel rods. No soil samples are collected using this method. Upon reaching the sample depth, the drill string will be removed,and a stainless steel bailer will be lowered into the open borehole. Approximately 200 milliliters(mL)of groundwater will be recovered,depending on formation permeability. The groundwater will be transferred immediately to 40 mL VOA vials,and labeled according to location,depth and time. After collection of adequate sample material, drilling will continue to the final depth, and the sampling procedure. t will be repeated., A duplicate groundwater sample will be collected from one location. Water samples will be analyzed for VOCs using EPA Method 8260B. The samples will be placed on ice immediately following collection,and kept in coolers until shipment to the laboratory for analysis. Samples will be delivered to the laboratory within one day of sampling. A chain-of-custody will be completed for each sample collected. The chairs-of-custody will include the sample identification,date and time of sample collection,sample collector's name, the project site name, analysis requested, and the signature, and inclusive time and date of sample. possession, of each person assuming possession of the samples. A copy of the chain-of-custody will be included in the sampling report. Sampling depths'of 40 and 55 bgs are anticipated. These depths are based in part on.the current depth to groundwater(approximately 44 feet bgs),and the geology at the site. Depth oriented samples are proposed in order to assess any potential concentration variations with depth,such as those observed at monitoring wells DMW-5 and DMW-6. Prior to drilling,the static water level at the site will be measured at the seven existing monitoring wells,and the target depths will be adjusted, if necessary_ Equipment decontamination will be conducted to minimize the potential for cross contamination between well r' locations. Prior to and after use,sampling and testing equipment will be washed in a non-phosphate(Alconox) solution,rinsed with potable water, and rinsed again with distilled water. Hard-bristle bottle brushes may be used in the first two wash buckets to remove mud and debris. Potable water will be obtained from on-site sources. Distilled water will consist of 5-gallon containers from a commercial supplier. No drill cuttings,are generated using the direct push methodology. Therefore, soil disposal will not be required. Because no drillings fluids are used,groundwater samples can be collected directly from the open borehole without pumping the well. Therefore,wastewater disposal will not be required. The drill holes will be abandoned immediately following the collection of the water samples. Abandonment will consist of grouting the borehole with a bentonite/cement slurry, using a tremie pipe. The surface will be repaired with asphalt. i KA840 MAFP\DCA_W ORKPt.AN.DOC t,