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�A l(V TC =" A S S O C I A T E S I N C 4.0 RESULTS 4_1 Petroleum Hydrocarbons in Soil Results of laboratory analyses performed on selected soil samples indicate that TPHd was not `= detected in the samples collected from boring MW7. Analytical results of soil samples are r: summarized in Table 1. 4_2 Petroleum Hydrocarbons in Groundwater .r fir= Results of laboratory analyses performed on groundwater samples indicated that TPHd was not detected in wells MW1 or MW6. TPHd was detected in monitoring wells MW2, MW3, MW4, 4 MW5, and MW7. Well MW4 contained the highest concentration of TPHd at 9,600 ppb. Well MW7, located furthest downgradient of the UST, contained TPHd at a concentration of 100 ppb. P-__ Analytical results of groundwater samples are summarized in Table 3. The estimated extent of TPHd in groundwater is shown on Figure 5. 5.0 CONCLUSIONS AND RECOMMENDATIONS Analytical results for soil samples from MW7 show that TPHd was not detected above its 12j, laboratory method detection limit. Analytical results of the groundwater samples indicate that the highest concentrations are southwest of the former tank location, which is consistent with f results of previous investigations and monitoring events. TPHd was detected only at a low concentration in the on-site downgradient well indicating that the plume appears to be stable and mainly confined to the site. Based on field observations, no free product was detected in any of the wells although a sheen was observed in well MW4. ATC recommends performing three additional quarterly monitoring events to obtain groundwater data. The monitoring events will each include collecting samples from all seven fir=- wells, analyzing the samples for TPHd, and preparing monitoring reports. Following the completion of the events, if the data show the plume is stable ATC will prepare an addendum to the previous request for closure report. F J F%;1 w:\Wordpro162574162574.021Reportslwell_install.doc 7