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I URS ISeptember 19, 2003 Page 4 I 21 Impact in Soil During the 1999 UST and product line removal and replacement activities, soil samples were collected from the bottom and side walls of the UST pit, the bottom of the product delivery line and vapor return line excavation trenches, and from beneath the dispenser islands Analytical results indicate contaminated soil at depths of 17 to 18 feet bgs in the northern, western, and southwestern areas of the UST pit Contamination was also present at the north end of the product delivery line (near VW-2 and the southwest corner of the UST pit) at depths of 5 to 7 feet bgs The highest concentrations detected in the soil in these areas were 11,000 milligrams per kilogram (mg/kg) TPHg, 272 mg/kg MtBE, 2 36 mg/kg tertiary amyl methyl ether JAME),�5 06 mg/kg benzene; "mg/kg toluene, 340 mg/kg ethyl benzene,"Q.9�4�Y mg/kg total xylenes, and total lead 63 9 rrnlligra s per liter (mg/L) (Pinnacle, 1999) 19an &1 .1)61 I m iQ.I -Q? 090 Mg J)(� I MtBE contamination was identified on the south and east sides of the UST pit at depths of 4'1'feet bgs, ; the concentrations were 0 131 mg/kg and 1 83 mg/kg, respectively The east wall sample also contained 0 0142 mg/kg of xylenesu p a�► �}�fG,1 ��i,,{o�1��f yv�,.� O IAnalytical results indicate that there is no contamination in the vapor return line trench which runs from the eastern side of the dispenser islands to the southeast corner of the UST pit (Pinnacle, 1999) _1 Figure 4 presents the extent of the soil contamination and a summary of the analytical results Attachment B presents geologic cross sections of the site and identifies soil types in the source area 2.2 Impact in Groundwater Impacted groundwater has been found beneath the site Figure 5 shows the extent of the groundwater ' contamination Table 1 presents groundwater analytical data TPHg and MtBE concentrations in VW-313 increased relative to historic data-MtBE concentrations increased in MW-I but were within historic ranges'Benzene concentrations continue to decrease in MW-1 All other analytes were reported I below laboratory detection limits Groundwater elevations in wells across the site generally increased — relative to the previous quarter The inferred groundwater flow direction was to the east-northeast at an average gradient of 0 01 feet/foot r�'accccuf� I�S t �w," 944d(C cf well 7 MW-1 is the only well at the site that has consistently shown elevated benzene concentrations'During the last sampling event on June 9, 2003 benzene was detected at 79 ICg/L;down from a high of 2,900 pg/]L from the September 12, 2002 sampling event",The 12-month period prior to the September 2002 sampling event exhibited similar benzene concentration behavior I MtBE has consistently been observed in wells MW-1,MW-4,VW-113, VW-2B, and VW-3B During the last sampling event on June 9, 2003 the MtBE levels for these wells has ranged from 810 µg/L at VW- 2B to 10,000 jig/]L at MW-1 I • K 1WprocessU5 BP ARCO1021861CAP Aug03%O2186 CAP03 doc