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W <br /> 1.2 PREVIOUS WORK <br /> Elevated-concentrations of total petroleum hydrocarbons in soil at the site <br /> were first noted in May of 1988, when the seven underground storage tanks were <br /> removed from the ground. During excavation, evidence of leakage from the tanks, <br /> including .soil staining by hydrocarbons, was relarted to have been observed. <br /> Although the total volume of hydrocarbons .released from the seven tanks is not <br /> known, roil staining had been observed to a c+apth of 15 feet below the ground <br /> surface. Analyses of nine soil samples obtained during UST removal c,2nfirmed <br /> that tho soils beneath several of tha excavated tanks contained hydrocarbon <br /> -• constituents. <br /> An initial site investigation was performed (Dames & Moore, January 1929), <br /> to determine the extent c-f hydrocarbon constituents observed in the soil during <br /> the tank excavations. This investigation included the installation of four, <br /> monitoring wells on-site (Figure 2); MW-1 at the former location of six of the <br /> underground storage tanks, MW-2 at the farmer location of the seventh underresnd <br /> tank (the waste oil tank), and MW-3 and MW-4 to the north of the UST locations. <br /> Water was first encountered between 22 feet to 27 feet below the ground surface <br /> during the initial investigation. Static water level was subsequently measured <br /> at approximately 19 feet below ground surface. Soil samples were collected <br /> during drilli.tg for well installation at five foot intervals and selected samples <br /> were aTtal;zed for hydrocarbons. Ground water samples collected from the four <br /> monitoring wells were analyzed for hydrocarbons ani chlorinated solvents. <br /> Thp results from the soil and water analyses showed that soil samples from <br /> 157-i and groundwatef samples from both MW-1 and MW-2, contained "elevated <br /> concentrations of hydrocarbons. Water s4mples from MW-] also shoved elavat..d <br /> levels of chlorinated solvents. No chlorinated so?.venla were dotected in water <br /> samples from MW-2, MW-3, or MW-4. As the data eollecteOL =ndicates a southerly <br /> gxcundweter gradient, a plume could -be expected to be moving south from the <br /> vicinity cf. MW-1. <br /> SF;CO3.001 2 November 1989 <br />