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As described in Section 4.2,the location of SB-14 was selected to assess groundwater <br /> conditions downgradient of previously identified soil affected with petroleum hydrocarbons. <br /> Residual petroleum hydrocarbon-affected soil was observed in soil samples collected <br /> coincident with the water table(i.e., approximately 35 feet bgs) from the soil core of SB-14, <br /> thus a grab groundwater sample was not collected. The visual presence residual petroleum, <br /> along with the detection of TPHc, BTEX, and PAHs in soil samples, indicate a separate area of <br /> petroleum hydrocarbon affected soil,beyond the area previously identified north of the former <br /> pump house(e.g., in the area of MW-1). Due to its location adjacent to the former pipeline <br /> right-of-way,the affected soil in the area SB-14 may be associated with operations of the actual <br /> pipeline. <br /> 5.3 GROUNDWATER RESULTS <br /> Approximately 3 inches of separate-phase petroleum hydrocarbons were measured in MW-1, <br /> which is slightly less than that measured in previous monitoring events. No separate-phase <br /> petroleum was detected in SB-13, MW-3,or MW-4 using the interface probe. Groundwater <br /> analytical results are shown on Figure 3. <br /> TPHd was detected in the groundwater samples collected from MW-2 and SB-13 at 97 µg/1 and <br /> 544 µg11(without silica gel preparation procedure), respectively. Following the silica gel <br /> preparation procedure, TPHd was not detected in the sample collected from MW-2 and <br /> detected at a concentration of 77 µg11 in the grab groundwater sample collected from SB-13. <br /> These results indicate that the material quantified as"TPHd"without the silica gel preparation <br /> procedure may be polar components that may be due to intrinsic bioremediation of petroleum <br /> near this location. Low concentrations of toluene and PAHs were detected in grab groundwater <br /> samples from SB-13 (i.e., at concentrations less than 1.0 µg11). <br /> TPHg,TPHd,BTEX, and PAHs were not detected in groundwater samples from monitoring <br /> wells MVV-3 and MW-4. TPHd was only detected in MW-2. <br /> 6.0 CONCLUSIONS <br /> Based on the results of this and previous investigations, Geomatrix has developed the following <br /> conclusions regarding site conditions. <br /> ■ The site is underlain primarily by fine grained deposits (i.e., silts)with interbedded <br /> coarse grained deposits(i.e., sands and gravel). The depth to groundwater as meas- <br /> ured in May 2002 ranges from approximately 36 to 37 feet bgs, slightly lower than <br /> xloaklWepWasalDuc_sare1SDO s15011.001\kq)or6SoiI and GW Reporndm 9 <br />