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TECHNICAL MEMORANDUM CKWILL <br /> Results of December 1996 Drilling, Stockton Former <br /> MGP Site <br /> PREPARED FOR: Patricia Sullivan/Pacific Gas and Electric Company <br /> PREPARED BY: Paula Bolio/CH2M HILL <br /> COPIES: Liz Dodge/CH2M HILL <br /> Thom Little/CH2M HILL <br /> DATE: February 5,1997 <br /> This technical memorandum outlines the objectives for the soil and groundwater <br /> investigation which took place at the Stockton former MGP site in December 1996, the <br /> analytical results of the sampling,and the conclusions and implications for the feasibility <br /> study. Figure 1 shows the boring locations. Figures 2-1 through 2-5 are revised figures <br /> which show soil borings located in Area I with their respective analytical results. Figure 3 <br /> shows borings located in Area II with their respective analytical results. Tables 1 through 5 <br /> present the analytical results from the sampling activities. <br /> Obj ectives <br /> The additional field work was designed to meet the following objectives: <br /> 1. Confirm/Modify Dimensions of Source Areas 1 and 4 <br /> -Data was collected to help define the vertical and horizontal extent of <br /> Source Areas 1 and 4 in Area I. This information will be used to confirm or <br /> modify the dimensions of these source areas. <br /> -This data will be incorporated into the VLEACH model and will result in the <br /> creation of additional polygons to further refine the model. <br /> 2. Determine leachability of COCs using the DI WET and TCLP tests <br /> -Selected soil samples were analyzed to determine leachability using the DI <br /> WET test for PNAs and TPH-diesel and the TCLP test to for TPH-gasoline <br /> and BTEX. The results will be compared with the VLEACH modeling <br /> results.The VLEACH model will be used to examine the potential <br /> downward movement of COCs from the vadose zone to groundwater. <br /> 3. Investigate source of diesel near MW-22R (Area II) <br /> -Further soil characterization was requested near soil boring location MW- <br /> 22R in Area TI. During the previous (Phase IV)investigation, Hydropunch <br /> sample results indicated that diesel was present in groundwater near the <br /> western comer of Area II.Diesel was not observed in the vadose zone above <br /> i <br />