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HEIMICN-f- IIRNIR Mr. Charles Leubner 30 January 1991 Page 4 _ for these compounds in all of the samples collected from the diesel tank excavation. In samples collected from the diesel tank's remote -fill pipe trench benzene, toluene, ethylbenzene, xylenes, and total petroleum hydrocarbons as diesel were all reported to be below the laboratory's respective limits of detection, except for sample No. 018. Sample No. 018 was the closest sample to the tank. Ethylbenzene and xylene were detected in this sample at reported concentrations of 4 ug/Kg and 30 ug/Kg, respectively (Table 1). _ All gasoline and gasoline constituents that were analyzed for in the sample collected from the 500 -gallon gasoline tank excavation were reported to be below the laboratory's limits of detection (Table 2). EVALUATION OF SOIL SAMPLING RESULTS A leaching potential analysis was performed for the 10,000 -gallon diesel tank using the method outlined in the October 1989 version of the Leaking Underground Fuel Tank (LUFT) Field Manual. Based on the assumptions shown in Table 3, the site scored 33 points. Using these evaluations, the reported maximum TPH concentration of 430 ppm from the 10,000 gallon tank excavation exceeds the recommended maximum allowable TPH as diesel of 100 ppm. The results of the laboratory analysis of the sample collected from beneath the center of the slab should be considered suspect due to the presence of water and mud in the bottom of the excavation resulting from a leaking water pipe adjacent to the excavation. The standing water and mud resulting from the water pipe leak was present in the hole that had been jackhammered through the slab for a period of several days previous to sampling. It is possible that soil containing hydrocarbons from other parts of the excavation may have been carried with the water through the hole in the slab and may have collected along with the native soil from beneath the slab. Thus, this sample should not be construed as indicating that the highest hydrocarbon concentrations are beneath the center of the slab. The second highest concentrations of diesel (290 mg/Kg) were reported in sample No. 017, collected from the northern side of the tank, near where the product supply piping to the building entered the tank. Other samples from the other corners of the excavation show low or no concentrations of petroleum hydrocarbons. Also, no holes were evident in the tank when it was removed from the excavation. These factors lead us to believe that the residual hydrocarbons detected in the excavation resulted from overspillage or leaking piping adjacent to the tank, and not a leak in the tank itself. Therefore, future investigations should concentrate on the northern side of the tank excavation.