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1 <br /> 2.0 CONCLUSIONS AND RECOMMENDATIONS <br /> Based on the scope of work performed during this investigation the following conclusions <br /> ' were developed <br /> 1 An undetermined amount of gasoline, but possibly as much as 1,200 gallons had <br /> escaped from one of the facility's three former 4,000 gallon underground storage <br /> tanks All three tanks were excavated and removed in April, 1991 Two of the <br /> three tanks were intact and showed only minor signs of deterioration The third <br /> tank however was believed to have been damaged as a direct result of a helium <br /> pressure test Although the age of the tanks is unknown, it is believed that they <br /> ' were installed before 1960 <br /> 2 Due to the interbedded nature of silt, sand and clay layers at the site, gasoline <br /> products including BTEX have traveled both laterally and vertically through the <br /> vadose zone soil The downward movement of the gasoline has reached the water <br /> table and has contaminated the groundwater immediately beneath the site. <br /> ' 3 The concentration of BTEX in theroundwater beneath <br /> g the site exceeds the <br /> respective MCLS for each constituent <br /> 4 Although the original source of the contamination e g the tank has been removed, <br /> a significant amount of vadose zone soil remains contaminated <br />' 5 No Iaterally continuous confining layer within the upper 35 feet of the soil column <br /> has been identified within the study area The upper aquifer material consists <br />' primarily of silt to fine-grained sand <br /> r6 Although the areal extent of the groundwater contamination has not been <br /> completely defined, the direction and velocity of groundwater flow has been <br /> quantified for the month of April, 1993 Because of the low hydraulic conductivity <br />' 4 <br />