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I ' z REQUEST FOR SITE CLOSURE REPORT -4- Former Beacon Station #610 3300 Waterloo Road, Stockton, California AMV Project No 19042 04 3.0 CURRENT SITE CONDITIONS 3.1 Current Distribution of Petroleum Constituents in Soil In September 1994, AMV advanced six additional soil borings at the site to depths ranging from 50 to 60 feet below grade Three of these bonngs were completed as 2 -inch -diameter vapor extraction wells (designated as VE -1, VE -2, and VE -3) Soil boring locations are illustrated on Figure 2. Existing monitoring well MW -7 was drilled out (including the PVC casing, grout, and gravel pack) on September 28, 1994, and a new 4 -inch -diameter monitoring well was installed within the resulting borehole Soil borings SB -4, SB -5, and SB -6 were terminated at 50 feet below grade, and soil bonngs SB -1, SB -2, and SB -3 were terminated at approximately 60 feet below grade Soil bonngs SB -1 and SB -2 were advanced within separate 16 -inch - diameter polyvinyl chloride (PVC) conduits, which were installed during the underground storage tank replacement in October 1993 Soil boring SB -3 was advanced at an angle of 30 degrees from vertical toward the northeast beneath the pump island area (Figure 2) • Four to six soil samples collected from each boring were submitted for analysis of concentrations of BTEX, TPHd, and TPHg Analytical results of soil samples submitted by AMV in September 1994 are summarized in Table 5 Only two soil samples submitted for analysis contained concentrations of BTEX and TPHg above the laboratory detection limit Soil samples SB2-7 and SB2-8, collected from soil boring SB -2 at 35 and 40 feet below grade, contained TPHg concentrations of 210 and 630 mg/kg, respectively Concentrations of benzene in these two soil samples were reported at less than 0 050 mg/kg Concentrations of TPHd in soil samples collected from soil bonngs SB -3, SB -4, SB -5, and SB -6 were reported to be less 1 0 mg/kg for all soil samples submitted for analysis. One soil sample collected from soil boring SB -1 (at 60 feet below grade) contained 27 ppm TPHd Soil samples SB2-7 (35 feet), SB2-8 (40 feet), and SB2-12 (60 feet), contained TPHd at concentrations of 1,700, 6,600, and 2 6 ppm, respectively • One soil sample collected from soil boring SB -2 at 40 feet below grade was submitted for laboratory analysis to assess the mobility of petroleum constituents in the soil beneath the site The test was performed for BTEX, TPHg, and TPHd Both tests involve placing sample material (soil) in a container and adding a measured quantity of liquid, in this case deionized water The sample is then agitated for a specified time period and the liquid is filtered and extracted The "extract" was then analyzed for the previously mentioned parameters Results of the "Wet DI" and "TCLP Extract" tests are presented in Table 6 As indicated in Table 6, benzene was not detected above the method detection limit in the extracted liquid Concentrations of TPHg and TPHd were reported at 2,600 and 55 jig/I, respectively 13QO11524 rpt114 m1