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MEW.... <br /> SECTION 3.0 <br /> 1 NATURE AND EXTENT OF CONTAMINATION <br /> 3.1 SOIL <br /> A summary of historical soil analytical data is presented in Table 6 0 Soil sample locations and <br /> the horizontal extent of soil contamination are shown on Figure 6. The extent of soil <br /> contamination is also shown on cross sections C-C' and D-D' (Figures 7 and 8) Based on <br /> data collected during the Phase III and IV investigations, there is approximately 7 to 8 feet of <br /> contaminated soil in the unsaturated zone Some contaminated soil may exist below the water <br /> table, but the actual level of contamination in the soil is difficult to separate from the <br /> contamination present in groundwater, since the samples were saturated <br /> 3.2 GROUNDWATER <br /> A summary of historical groundwater analytical data is presented in Table 7 Groundwater <br /> contaminant levels have decreased significantly In the 26 months between initial sampling of <br /> MW-2A (July 1995) and the most recent sampling event (December 1997), benzene <br /> concentrations have decreased from 7,000 µg/L to 200 µgIL and TPH-G concentrations have <br /> decreased from 79,000 jcg/L to 1,400 pglL The estimated extent of benzene contaminated <br /> groundwater, based on the most recent complete round of groundwater samples available, is <br /> presented on Figure 9 <br /> 3.3 PHYSICAL AND CHEMICAL CHARACTERISTICS-_O_F CONTAMINANTS <br /> Gasoline is therimar contaminant at the site Although gasoline is composed of over 200 <br /> P y <br /> compounds, benzene, toluene, ethylbenzene, and total xylenes (BTEX) are the constituents of <br />' primary concern Some basic properties of these compounds are listed below in Table 8. <br /> • <br /> LTROJUCMSASJOQ1HSMAC 10NPL 15 <br />