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3.2.5 Soil Sampling Strategy The strategy of the soil sampling plan was to delineate the extent of the contamination previously identified within the Site. All soil samples were analyzed for PAHs, TPH, and Title 22 Metals. Selected soil samples were analyzed for VOCs and for geotechnical parameters in order to generate the data necessary to meet the needs of the baseline HRA. Twelve soil borings were placed to delineate the lateral and/or vertical extent of impacts identified during previous investigation or the RI at the Site as shown in Figure 9. The remaining three borings (A3-1, A3-2 and C2-1) are located in areas adjacent to the location of the former MGP gasholder base and the former gasoline UST. Note that only readily accessible portions of the Site (exterior paved areas)were sampled during this investigation. At each soil boring location, continuous soil samples were collected for lithologic description. Discrete soil samples were collected from depths of 1, 3, 5, and 8 feet bgs (depth of first encountered groundwater), where applicable. At one location (Boring E3-1), soil samples were collected to a depth of 15 feet bgs. In addition, where impacts were encountered, additional soil samples were collected. Where field evidence (staining or odor) of contamination was encountered during sampling, deeper soil samples were collected until the vertical extent of impacted soil could be determined. At one additional location, A3-2, soil samples were collected to a depth of 25 feet bgs and then monitoring well TW-5 was installed. Boring TB-13 showed the highest PAH impacts during previous investigation (Figure 6). Two soil borings (A 1-1 and BI-1) were placed in close proximity to TB-13 to determine the lateral extent of identified impacts. In addition, Borings Cl-1 and Dl-1 were placed to delineate impacts associated with previous investigation Borings TW-2 and TB-16. At each of these three locations (TB-13, TW-2 and TB-16), impacts were encountered at a depth of 2 to 2.5 feet bgs and samples collected at deeper depths showed no PAH impacts. Hence, vertical delineation was achieved at each of these locations. Additionally, Borings BI-1, Cl-I, and DI-1 were used to assess the potential impacts at the property boundary on the east side of the Site. Borings A2-1 and A3-2 were advanced to delineate the potential lateral and/or vertical impacts that were described in the previous gasoline UST investigation boring logs for Wells OW-1 and OW-2. These potential impacts were not sampled and/or analyzed during previous investigations; however, the description of the impacts in the boring log for OW-1 states that "lampblack" was located approximately 2 to 8 feet bgs and "lampblack" was described at approximately 2 feet bgs in the OW-2 boring log. Boring A3-2 was also used to delineate potential impacts downgradient of the former gasoline UST, which was located near the northwest corner of the warehouse and was removed in 1987. Monitoring Well TW-5 was installed at the A3-2 location to monitor potential residual impacts in groundwater from the gasoline UST. Boring A3-1 was installed to delineate the potential impacts upgradient of the former gasoline UST. Boring 132-1 was placed adjacent to the southeast corner of the existing building at the Site to investigate an area not sampled during previous investigations. Boring C2-1 was placed to delineate potential impacts near the location of the gasholder base from the former MGP operations. The location of Boring E2-2 was selected to identify potential lateral impacts that were not delineated in previous investigation Borings TB-21 and TB-22. Boring D3-1 was placed between the western property boundary and previous investigation Boring TB-26 to PARSONS 27 FINAL RI REPORT-FORMER TRACY MGP APRIL 2010