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i ' MtBE in soil from 10 to 19 5 feet bgs There are not enough data points below 20 feet bgs to interpret the lateral extent of MtBE in the deeper soils The lateral distribution of MtBE in soil from 10 to 19 5 feet bgs appears well delineated to the east by MW-3 and MW-4, to the ' south by MW-1, and to the west by MW-7 Due to the presence of MtBE in soil samples collected from MW-8 and MW-9, the northern extent of MtBE in sod is not defined Figure 9 depict the vertical extent of MtBE concentrations in soil and shows the source area ' as the dispensers and UST pit with a smear zone spreading out from the source area in the direction of the groundwater flow ' 5.2 Distribution of Hydrocarbons in Groundwater BTEX, DIPE, EtBE and 1,2-DCA have not been detected in any groundwater samples ' collected from-this site (Table 3) TPHg was detected in one groundwater samp a ocl llected rom CPT-1, however, the result was suspect, and upon further investigation and review of the chromatogram it appears that the detection was of 2-ethyl-l-hexanol, which is commonly ' associated with pipe dope and is not a typical constituent of gasoline or diesel fuel (Table 3 and Appendix F� 1_--�_-- - ' TBA was detected in groundwater samples collected from the UST excavation and from MW- 5 but has not been detected since the first quarter 2004 TAME was detected in groundwater samples collected from the UST excavation, MW-2, and MW-5, as well as during the pump test (EX-1) but was not detected in groundwater samples collected from the monitoring wells during the third quarter 2004 ' MtBE is the only dissolved hydrocarbon detected in groundwater samples collected during the third quarter 2004 SECOR plotted the lateral distribution of MtBE concentrations in shallow groundwater for the ' subject site, along with data collected from the Shell station located north of the site, and included the results as Figure 10 The wells belonging to the former Grant Line Gas & Food (currently Valero) have not been monitored or sampled since June 2003 and were not used ' in contouring Figure 10 shows that the highest concentrations of MtBE are present in the north section of ' the property near MW-5 and the newly installed remediation test wells MtBE concentrations are delineated to the south, east, and west The plume appears to have expanded to the north and northeast in the direction of groundwater flow until merging with the Shell MtBE plume source area The most downgradient well (MW-8) contained 210 uglL MtBE during the third quarter 2004 (Table 3) Figure 11 depicts the lateral and vertical extent of the MtBE plume along the axis of ' groundwater flow and shows the highest reported MtBE concentrations in groundwater are immediately downgradient of the LISTS (Cross Section A-A') and dispenser islands (Cross Section B-B') 1 � 32262 Assessment&Feasibility Report&SCM doc 8 September 30 2004 ' 77EL 32262 04 0502