SITE INFORMATION AND CORRESPONDENCE

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9110 Thornton Road Page 2 During 1992,groundwater contamination was detected in samples collected from monitoring wells, MW1, MW9, and MW18. Groundwater samples should continue to be collected quarterly from all monitoring wells. Please be informed that PHS/EHD inspection of sampling events are an important aspect of local regulatory oversight. For confirmation sampling events PHS/EHD inspections are essential. Please contact Mary Meays at the number indicated below, at least 48 hour prior to any future sampling events. SOIL CONTAMINATION The results of the soil investigation, prior to confirmation soil sampling (January and February 1993) were not included in the closure report. PHS/EHD staff with assistance from Groundwater Technology attempted to summarize the analytical results from the soil investigation. In order for PHS/EHD to evaluate the site for closure certification, a more comprehensive summary of soil analytical results will be necessary. In May 1986, a limited excavation around the product lines indicated that a leak likely occurred in a line under the cement pad at the pump island. The investigation of the leak which commenced evidenced both soil and groundwater contamination. Soil contamination was evidenced by laboratory analysis during the installation of MW2, MW3, MW4, MW9, MW11 MW12, MW20, RW2 (recovery well) RW3, VP2 (vapor well) VP3, and VP4. Petroleum hydrocarbon visual observation or odor was noted during the installation of MW1, MW2, MW3, MW4,.MW9, MW10, MW11, .MW12, MW14, MW20, PW1 (pumping well) PW2, VP2, VP3, VP4, SBI (soil boring). A vapor extraction system to remove hydrocarbons from the subsurfacebegan operation in February 1987 and continued until January 1991 when the system was shut down. Over 3,800 pounds of gasoline (576 gallons) were reportedly extracted from the soil and shallow groundwater utilizing RW1, MW1, MW3, MW4, VP1, VP2, VP3 and VP4. Samples collected in January 1991 from MW1 and MW4 still,evidenced gasoline contamination in the vapor phase. No final samples were collected from RWI, MW3, VP1, VP2, VP3, or VP4 to evidence the completion of vapor extraction remediation. Please provide information regarding the expected radius of influence for the system which was operated. Confirmation soil samples were collected January and February 1993. While the analytical results did not indicate soil contamination, with the exception of SP1, both PHS/EHD staff observations and field screening (PID >.5 ppm) did indicate residual soil contamination. Nine soil borings were drilled and sampled, SB(A) - SB(J). Soil contamination was observed during the drilling of SB(C) SB(D) SB(E) SB(F) and SB(J).