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0 <br /> solvents, and aromatic chlorinated compounds. Tank-content history <br /> ' is thus reasoned to have been exclusive to diesel/bunker-fuel oil <br /> product. <br /> ' The mode of tank-content product release to the surrounding <br /> soils was visually obvious once the steel tanks were uncovered, <br /> ' thereupon revealing the presence of holes within the tank walls. <br /> Since the tanks have been out of service and abandoned for many <br /> ' years, the volume of product that has been released is unknown. Any <br /> documentation or past records of tank-use history to this effect are <br /> not known to exist. However, some product escape has occurred via <br /> ' the holes in the tanks as substantiated by the TPH analysis. <br /> ' The full extent and magnitude of product concentrations in the <br /> soils about the vicinity of the tank cluster would require additional <br /> testing of the subsurface soils. Additional testing would also help <br /> ' delineate the thickness and aerial extent of the lower clay unit in <br /> which the tanks resided. This determination may prove critical in <br /> defining the depth of product migration through the highly <br /> ' impermeable clay layer. <br /> ' Even though fluids can migrate through "tight' clay layers, the <br /> process is very slow through time. Therefore, it is likely that <br /> migration of escaped product has not traveled far from the source <br /> ttanks if the clay layer is thick and laterally extensive. <br /> ' The extent of product presence in soils beneath the concrete- <br /> tank vault is minimal. The one soil sample from beneath the vault <br /> nearest the adjacent steel tank showed a relatively low TPH <br /> ' concentration. This finding may support the reasoning of slow and <br /> thus, minimal migration of product released from the nearby steel <br /> ' tanks throughout the underlying clay unit. <br /> 6.0 RECOMMENDATIONS <br /> ' 1 . A site assessment investigation is recommended for the <br /> area in proximity to the tanks removed from the Scotts Avenue <br /> ' locality. Further testing of the soils would help delineate the <br /> presence or absence of product plumes. <br /> 8 <br />