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GEOMATRIX was slightly above the laboratory practical quantitation limit of 0 5 pglL Oxygenates have ' not been detected in the soil and groundwater samples collected from the site during previous site investigations Since DIPE has not been detected in the samples previously collected from the site and no TPHg was detected in this sample, the detection is likely a false positive and not representative of the groundwater quality at 40 feet bgs at this location Dissolved lead 1 (analysis requested by PHS/EHD) was detected at a low concentration of 4 3 µg/L These analytical results are consistent with the previous site characterizations and indicate that the vertical extent of groundwater affected by petroleum hydrocarbons is limited to less than 40 feet bgs at the site These analytical results also confirm that the TPHg and BTEX detections in the grab groundwater sample collected at about 41 feet bgs from boring B3-5 in ' 2001 was a result of cross-contamination and not representative of groundwater quality at this depth tOxygenates and 12DCA were not detected in the groundwater samples collected from the ' three new monitoring wells (Table 5 and Appendix B), these results are consistent with previous site data The concentrations of dissolved lead in the groundwater samples collected from the three new monitoring wells ranged from less than 3 to 3 7 pg/L TPHg and BTEX Mwere not detected in the groundwater samples collected from MW34 and MW3-5 TPHg and BTEX were detected in the groundwater sample collected from new well MW3-6 TPHg and ' BTEX concentrations in the groundwater samples collected from the three existing wells are within historical ranges Based on the analytical data of the groundwater samples, the estimated lateral extent of groundwater affected by petroleum hydrocarbons as result of the UST release is shown on ' Figure 2, and the estimated vertical extent of affected groundwater is shown on Figures 8 and 9 The maximum vertical extent of affected groundwater at the site is limited to a depth ' between about 13 and 35 feet bgs The lateral extent of groundwater affected by petroleum hydrocarbons is limited to an area of approximately 150 feet wide and 200 feet long. 4.5 SITE CONCEPTUAL MODEL ' A release of gasoline-based PHCs to soil and groundwater in the vicinity of Site No 3 has been attributed to two USTs that were removed from the site in 1988 Approximately 180 cubic yards of affected soil were excavated and removed at the same time Analytical ' results of soil and groundwater samples collected from the site indicate that the released I TROJECA60WA6437 00016437-08400 1 1