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Mr. Michael Walton Walton Engineering March 20, 1998 The laboratory analytical results of soil samples collected from the two sidewalls and base of the area of overexcavation indicated that concentrations of TPHd were significantly reduced by the excavation work. TPHd was not present in the sidewall soil samples collected from approximately 17 feet below ground surface on the western sidewall, while only a low concentration of TPHd was detected at approximately 19 feet on the northern sidewall (Table 2). The soil sample collected from the base of the open excavation at approximately 24 feet below ground surface was found to contain slightly elevated concentrations of TPHg and xylene isomers and a residual concentration of TPHd at 230 ppm. This residual concentration of TPHd, however, had been mitigated from an initial concentration of 22,000 ppm by the excavation work (Table 2). The laboratory reports for these soil samples are presented in Appendix. GRAYLAND ENVIRONMENTAL Grayland 022-160.trr 5 TABLE 1 LABORATORY RESULTS OF SOIL SAMPLE ANALYSES UNDERGROUND FUEL STORAGE TANKS EMENEEMEMEMINIM 3300 WEST LANE, STOCKTON, CALIFORNIA Storage Tanks S-17-T1n 83 0.750 <0.050 0.640 1.40 22,000 6.7 S -16 -T1s <1.0 <0.005 <0.005 <0.005 <0.010 <1.0 8.1 S-13-T2n <1.0 <0.005 <0.005 <0.005 <0.010 na 7.9 S -16 -T2s <1.0 <0.005 <0.005 <0.005 <0.010 na <5.0 S-14-T3n <1.0 <0.005 <0.005 <0.005 <0.010 na na S-17-T3s <1.0 <0.005 <0.005 <0.005 <0.010 na na Fuel Dispensers S-4-FD1 1.2 <0.005 <0.005 <0.005 0.020 na na S-3-FD2 <1.0 0.024 0.099 0.013 0.150 na na S-3-FD3 <1.0 <0.005 <0.005 <0.005 <0.010 na na S-4-FD4 <1.0 <0.005 <0.005 <0.005 <0.010 na na S-3-FD5 <1.0 <0.005 <0.005 <0.005 <0.010 na na S-4-FD6 <1.0 <0.005 <0.005 <0.005 <0.010 na na Product Pipelines S -4 -PL 1 <1.0 <0.005 <0.005 <0.005 <0.010 na na S-3-PL2 <1.0 <0.005 <0.005 <0.005 <0.010 <1.0 na S-4-PL3 <1.0 <0.005 <0.005 <0.005 <0.010 <1.0 na S-4-PL4 <1.0 <0.005 <0.005 <0.005 <0.010 <1.0 na S-3-PL5 <1.0 <0.005 <0.005 <0.005 <0.010 <1.0 na Laboratory results of the soil samples are reported in milligrams/kilogram (parts per million) TPHg = Total Petroleum Hydrocarbons in the range of gasoline TPHd = Total Petroleum Hydrocarbons in the range of diesel fuel < = Less than the laboratory method reporting limit na = not analyzed The laboratory analytical results of soil samples collected from the two sidewalls and base of the area of overexcavation indicated that concentrations of TPHd were significantly reduced by the excavation work. TPHd was not present in the sidewall soil samples collected from approximately 17 feet below ground surface on the western sidewall, while only a low concentration of TPHd was detected at approximately 19 feet on the northern sidewall (Table 2). The soil sample collected from the base of the open excavation at approximately 24 feet below ground surface was found to contain slightly elevated concentrations of TPHg and xylene isomers and a residual concentration of TPHd at 230 ppm. This residual concentration of TPHd, however, had been mitigated from an initial concentration of 22,000 ppm by the excavation work (Table 2). The laboratory reports for these soil samples are presented in Appendix. GRAYLAND ENVIRONMENTAL Grayland 022-160.trr 5