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33 Distribution of Gasoline Hydrocarbons in Soil and Groundwater <br /> 3 3 1 Soil Sample Anal ical Results <br /> In soil, the highest concentrations of gasoline compounds were observed at a depth of 15 feet <br /> near the former UST Based on the results of soil samples collected at 20 and 25 feet bgs near <br /> the former UST, the vertical extent of impacted soil was defined to a depth of approximately 20 <br /> feet bgs Laterally, the extent of impacted soil appears to be limited to the vicinity of the former <br /> UST system The cumulative soil sample analytical results are summarized in Table 1, and the <br /> distribution of gasoline in soil is shown in cross-section (Figure 6) <br /> 3 3 2 Groundwater Sample Analytical Results <br /> On March 24, 2004, the groundwater sample collected from MW-1 contained 29,000 micrograms <br /> per liter (µg/1) of TPH-as-gasoline, 1,900 µg11 of benzene, 280 µg11 of toluene, 2,000 µg11 of <br /> ethylbenzene, 6,800 µg11 of xylenes, and 13 µg/l of MTBE The groundwater sample collected <br /> from MW-3 contained 0 5 µg/l of MTBE This was the first gasoline compound detected in MW-3 <br /> in seven quarterly groundwater sampling events <br /> On June 18, 2004, all throe wells contained detectable concentrations of MTBE The sample <br /> collected from MW-1 contained 11,000 µg/l of TPH-as-gasoline, 710 µg/l of benzene, 35 µg/l of <br /> toluene, 940 µg/l of ethylbenzene, 2,600 µg/l of xylenes, and 10 µg/I of MTBE MTBE was <br /> detected in MW-2 at 1 1 µg/l and in MW-3 at 4 2 µg/l The groundwat@@r sample analytical results <br /> b6 zo-&a,,MTL4& <br /> are summarized in Table 2, and the distribution of gasolineAn groundwater is shown on Figure 7 <br /> 34 Hydrocarbon Mass Calculations �'oy <br /> 3 4 1 Sorbed Hydrocarbon Mass in Soil <br /> Based on the cumulative soil analytical results, impacted soil appears to be limited to the vicinity <br />' of the former UST and underground piping The estimated volume of impacted soil is a <br /> rectangular prism approximately 60 feet long, 15 feet wide, and 5 feet thick As outlined in Table <br /> 4, the hydrocarbon mass calculations (in pounds) are <br /> 1 T ' <br /> PH_Gasoline Benzene Toluene Ethylbenzene Xylenes MTBE <br /> 29407 016 615 5 00 26 23 0 01 <br /> 9 <br /> r <br />