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�} INTERNATIONAL TECHNOLOGY CORPORATION 1 1 1.0 Introduction IT Corporation (IT) was retained by Pacific Bell to execute the venfication monitoring program proposed in the IT Corporation, Site Investigation Report, Pacific Bell, Facility No UE042, 345 North San Joaquin Street, Stockton, California, March 1992 The verification monitoring program consists of the sampling and analysis of groundwater samples collected from three on-site monitoring wells This report summarizes the quarterly monitoring event conducted during March 1992 2.0 Site Background The Pacific Bell facility located at 345 North San Joaquin Street in Stockton consists of a building which covers the entire site (half a block) In December 1990, two diesel UST's (300 gallon and 550 gallon) located beneath the basement floor in the center of the facility building were closed in place by filling with a cement slurry Several borings were hand bored beneath the tanks and total petroleum hydrocarbons expressed as diesel were found in the soil as high as 22,000 ppm. In December 1991, IT corporation installed three monitoring wells in the streets around the site (Figure 2). In the soil samples analyzed, no total petroleum hydrocarbons as diesel, was observed, however in the upgradient boring TPH as gasoline was observed (7.4 ppm) Benzene, toluene, ethyl benzene, & xylenes (BTEX) were identified in soil samples in MW-1 (downgradient) and MW-1 (upgradient) �} BTEX constituents were not observed in any of the groundwater samples The groundwater �I samples from MW-1 and MW-2 contained 130 ppb and 52 ppb TPH as diesel, respectively (Table 3). 3.0 Quarterly Activities The wells were sampled and groundwater elevations recorded on March 30, 1992 (first quarterly event) Water-level data was collected so gradient and flow direction could be 1 4