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in Figure 6. The sample was carefully inspected for visual impacts. The sample was transported to McKesson Environmental Services Laboratory in Pleasanton, California, for analysis. Based on the results of this sample, the PA made the determination that the Site did not warrant interim management measures or immediate in-depth characterization (PG&E, 1986). 2.5.4.2 Underground Storage Tank Investigations Three investigations, conducted subsequent to the PA, were implemented at the Site. These investigations focused on a 1,500 gallon gasoline UST that was located at the northwest corner of the Site near the existing PG&E Service Center building. The three investigations focused individually on soil, soil gas and groundwater impacts associated with the gasoline UST, which was installed in the early 1960's (PG&E, 1989). Boring locations and vapor monitoring points are shown in figures 6 through 8. The first investigation was conducted in November 1986 and reported floating gasoline product on the groundwater table in two borings (B-1 and B-2) drilled within 5 feet of the gasoline UST. Lead and BTEX were detected in soil and grab groundwater samples collected from the two borings. The locations of these two borings, along with the historically detected COPCs in soil are provided in Figure 6. Analytical results for these soil and groundwater samples collected as part of this investigation are provided in Tables 2 through 5 (soil) and Tables 7 through 10 (groundwater), respectively. As a note, the gasoline UST was removed in October 1987 along with impacted soil and floating product(PG&E, 1989). A second investigation conducted in June 1987 consisted of the installation and sampling of thirteen vapor monitoring points (VI through V13) surrounding the gasoline UST. Samples were collected from each of these vapor monitoring points and analyzed using a portable gas chromatograph (GC) calibrated to benzene and toluene. Results from portable GC showed concentrations of benzene and toluene greater than the detection limit of 1 part per million (ppm) in vapor monitoring points V2, V5 and V7. Concentrations of benzene ranged from 5.0 ppm in V7 to 1,000 ppm in V2. Toluene concentrations ranged from 10.0 ppm in V5 to 900 ppm in V2. Data generated with the portable GC also identified "peaks prior to benzene" and "peaks otherwise not identified". Because the portable GC was not calibrated to these "peaks" they could not be reported as individual constituents. The range of concentrations for peaks prior to benzene was 14.0 ppm (V5) to 11,600 ppm (V2) and the range for peaks not otherwise identified were 25.0 ppm(V5) to 3,000 ppm(V2). The locations of the vapor monitoring points along with the historically detected COPCs in soil gas during this event are provided in Figure 7. Analytical results for these soil gas samples are provided in Table 6 (PG&E, 1989). In December 1987/January 1988, a third investigation was conducted after the gasoline UST was removed. The goal of the third investigation was to further quantify the lateral and vertical extent of the hydrocarbons in soil and groundwater surrounding the former gasoline UST. This investigation consisted of drilling and sampling six observation wells (OW-1 through OW-6), which were placed within 80 feet of the former gasoline UST location. All six observation wells were sampled for BTEX, cyanide, general minerals, PAHs, pH, phenols, sulfides, Title 22 Metals, and total petroleum hydrocarbons (TPH) as gasoline, diesel, and motor carbon chain oil ranges. Impacts were generally limited; however, there were some concentrations above laboratory reporting limits. Of particular importance to note, groundwater sampled from observation well OW-2 had elevated concentrations of BTEX and total petroleum hydrocarbons PARSONS 16 FINAL RI REPORT-FORMER TRACY MGP APRIL 2010