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19 May 1997 AGE-NC Project No. 96-0266 Page 2 of 8 2.3. PREVIOUS INVESTIGATIONS At the request of the Union Safe Deposit Bank,a subsurface investigation was conducted at the site on 14 November 1996 and 16 January 1997. The investigation focused on both the areas of the former UST located within the City'of Stockton right-of-way and the existing UST located within Building C and Building I a metals plating shop. The investigation was performed to determine if hydrocarbon-impacted soil and/or ground water was present at the site and.if metals had impacted the site, especially the area surround the planting shop. A total of fifteen soil probe borings (P1 through P15) were advanced at the site, under the supervision of the PHS-EHD. Two soil probe borings were advanced in the vicinity the UST located within Building C; six soil probe borings were advanced in the vicinity the UST removed in 1986, formerly located in the City of Stockton right-of-way; three soil probe borings were advanced near the southwestern edge of the site; and four soil probe borings.were advanced in the vicinity the plating shop on the site. Locations of the soil probe borings are illustrated on Figure 2. 2.3.1. FINDINGS Tan and brown, silty clay was encountered in each probe boring from surface grade to depths of approximately ten feet bsg; gray, silty sand was encountered at depths between 10 and 15 feet bsg. Coarse-grained sand to gravel was distributed below the .silty sands, from depths of 15 to approximately 19 feet. Finally, a gray silty clay was encountered at a depth of'twenty feet in most probe borings. TPH-g, BTE&X and MTBE were detected in soil samples collected from probing P1 at concentrations as high as 3,700 mg/kg(milligrams per kilograms or parts-per million:ppm). TPH-g, toluene,ethyl benzene and xylenes were also detected in one soil sample collected from probing P 12, at concentrations up to 61 ppm. Petroleum hydrocarbons were not detected in soil samples collected from any other probings advanced during this investigation. TPH-g was detected in four of ten grab ground water samples collected from the UST area at concentrations ranging from 84 to•44,000 yg/l (micrograms per liter or parts per billion: ppb). BTE&X were detected in six of ten samples analyzed at concentrations ranging from 0.60 to 7,800 ppb. TPH-d was detected in four of five grab ground water samples analyzed at concentrations up to 6,600 ppb(P14). The approximate lateral extent of dissolved hydrocarbons are depicted on Figure 3 -Dissolved Hydrocarbons in Ground Water. A total of nine soil samples collected from the plating shop area were analyzed for LUFT metals (cadmium, chromium,lead, nickel and zinc).Additionally, 'one,sample each from probe borings P2