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Harding Lawson Associates U7.0 CONCLUSIONS Results of this investigation,-including HLA's review of LF's November 9, 1989, report on the,tank;removal, indicates that a release of petroleum hydrocarbons had ti occurred at the°site in the vicinity of the dispenser and had impacted the soil in that area. Analysis of soil samples collected from the floor and walls of the excavation in the former dispenser location during this investigation reported no detectable concentration of TPH or BTEX, with the exception of a low concentration of motor.oil ",'in the southern wall'of the excavatlon� 'Detectable concei trations"of TPH as'gasoline,° Li �diesel and motor oil, a.nd.xylenes.were repotted in the composite samples.from..the .stockpiles: On the basis of the analytical results of the excavation floor and wall samples it appears that the excavation has removed the majority of soils containing detectable concentrations of petroleum°hydrocarbons, and no significant concentrations of petroleum hydrocarbons remain in the native soil at the site. ! Results of-the field investigation and literature review indicate that the site is underlain primarily by low and moderate permeability sediments with a depth to � .groundwater of approximately 50 to 60 feet. The preceding information indicates that the soils impacted originally by the release at the site contained petroleum hydrocarbons, were separated from the groundwater table by approximately 45 to 55 feet and'have now been removed. Only Lv motor oil, a petroleum hydrocarbon of low mobility, hashbeen.detected in the soil in the' a r southern- wall of the excavation.'However, the reported concentration of motor oil does not exceed the method detection.limit by the range of accuracy of the analysis; therefore, the reported value may be the result of laboratory error and not accurately L T19461-H 17 of 20 i