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, TreadwelEADI D of 41 samples). In addition, in only 3 % of the results, TPH-kerosene concentrations have been reported to be greater in magnitude than the corresponding TPH-gasoline result from soil and groundwater (3 out of 86 samples) . Based on this data and historical evidence indicating that the USTs did not contain Kerosene, TPH-k does not appear to be a contaminant at the Site. Based on the age of the release, it is estimated that1 MTBE and fuel oxygenates were not present in ( '0{th s gasoline released at the site. This is further supported by the general absence of these compounds in k Site soil and groundwater. Sporadic, low concentrations of MTBE and a few oxygenates have been r detected, but not at a frequency or concentration to classify them as contaminants of concern . For example, MTBE has been detected in six of the fifty-six water samples collected at the Site at concentrations ranging from 1.5 to 3. B pg/L, which is lower than the Maximum Contaminant Level for drinking water of 13 pg/L1 j 7. 2 Extent of Groundwater Impacts. The lateral distribution of TPHg and benzene in the shallow zone groundwater are shown on ' - - Figures 5 and 6 respectively. These figures indicate that the shallow source plume is largely located within the vicinity of the former pump station and distribution lines. The extent of contaminant migration in the shallow zone does not appear to extend more than 50 feet down-gradient of the former USTs based on investigations performed thus far. ( l Petroleum hydrocarbon impacts are greater within the deep zone. The lateral distribution of TPHg and benzene in the deep zone groundwater are shown on figures 7 and 8 respectively. Significant concentrations of TPHg and BTEX appear to be distributed over a larger area than within the shallow zone. The contaminant distribution suggests that the direction of groundwater gradient in the deep zone is likely to the north-east, however, no wells have been placed in this zone, so an accurate groundwater flow direction and gradient has not yet been identified, and therefore the lateral extent of contamination has not yet been established. % 8.0 PROPOSED GROUNDWATER MONITORING This work plan proposes to install six monitoring wells at four locations (MW-5s, MW-5d, MW-6s, MW-6d, MW-7s, and MW-8d) as shown on Figure 9. The well locations were selected to better characterize the 12 25971201 . DGD 6 February 2008