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NNOW <br /> WEISS ASSOCUI7ES <br /> J.Munoz/ 11 August 1988/ Page 2 <br /> spread at the rear of the Safeway facility with the hydrocarbon-bearing pea gravel <br /> previously removed from the excavation. Since the southern side of the excavation was <br /> close to Navy Drive, after soil samples were collected, clean soil backfill was placed <br /> against the southern side of the excavation to reduce the likelyhood of slope failure. <br /> SOIL SAMPLING AND ANALYSIS <br /> During digging, six samples of native soil were collected from the walls and floor of <br /> the excavation between depths of 14 and 24 ft. Nine samples of the previously excavated <br /> pea gravel were also collected from the stockpiles at the rear of the Safeway facility. All <br /> the samples were analyzed by EPA Method 8015, gas chromatography with flame <br /> ionization detection (GC/FID) for total petroleum hydrocarbons (TPH). Analytic results <br /> for the native soil samples ranged from less than 10 parts per million (ppm) TPH to 3700 <br /> ppm TPH. The nine pea gravel samples were combined into three composite samples for <br /> analysis. Analytic results for the pea gravel composites ranged from 29 ppm TPH to 180 <br /> ppm TPH. Tabulated analytic results and laboratory analytic reports for these samples, as <br /> well as a summary of all previous work, will be presented in a comprehensive report <br /> prepared after final closure of the excavation. <br /> CONCLUSIONS <br /> Observations of hydrocarbon staining and odor and the analytic results for the <br /> native soil samples suggest that hydrocarbons in native soil begin at about fifteen ft <br /> below ground surface and may extend laterally away from the excavation and vertically <br /> downward a greater distance than previously indicated. The limits of the high <br /> hydrocarbon concentrations were not determined during this phase of the investigation. <br /> Analytic results for the pea gravel composites suggest that detectable concentrations <br /> of hydrocarbons remain in the pea gravel. This material cannot be used as backfill for <br /> the tank excavation until additional sampling and analysis indicates no detectable <br /> hydrocarbons in the pea gravel. If this additional sampling and analysis indicates that <br /> aeration is not adequately reducing the hydrocarbon concentrations, alternative remedial <br /> options for the pea gravel will need to be explored. <br /> RECOMMENDATIONS <br /> Since the proximity of Navy Drive to the southern wall of the excavation may <br /> interfere with continued excavation, the vertical and horizontal extent of hydrocarbons in <br /> soil should be determined before excavation resumes. If this further definition indicates <br /> that continued excavation is not the most effective approach for remediating the <br /> remaining soil, alternative remedial options will be assessed. Our recommended scope of <br /> work to further define the extent of hydrocarbons in soil is to: <br />