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native soils within the tank bed, and there was little threat to groundwater, it was used to backfill the excavation (It has been Time Oil's intent to assess and remediate this soil concurrent with the remediation of the former tank bed ) Soil and Groundwater Investigation Base��ie ,an�.,l,,yti.cal results of the soil samples collected during the tank removal, a site assessment sated in Auiist 3�T9to -eterrnina the extent of`contamination at the above-referenced site Prior to the implementation of fie d activities, Canonie's workplan dated July 24, 1992 was submitted for your review Authorization to proceed with the proposed work was received from the Environmental Health Division on August 4, 1992 On August`_iL9�2,— -sQil yap�surve -y�as performed to assist in determining the vertical and lateral extent of contamination at the subject site A pneumatic hammer was utilized to drive 13 soil vapor probes to depths of up to 13 feet in the vicinity of the former tanks Vacuum pumps and charcoal tubes were used to collect vapor samples from each probe at various depths Immediately after collection, each sample was submitted to an onsite mobile lab where it was extracted and injected into a gas chromatograph Due to the presence of hardpan just below the ground surface, the results of the soil vapor survey were fairly limited, as no probes could be advanced deeper than 13 feet The survey verified the presence of contamination within the former tank bed and suggested that the hardpan layer had not been affected A copy of the soil vapor survey report is included as Appendix B of the site assessment report During the week of September 28 , 1992, a mobile drill ri was utilized to advance dour i n ree �pno extr io e is and insta t ree vapor in et we s Aur ng fie d activiso were found to con ar pan to a depth of approximately 15 feet, this strata was underlain by loose fine to medium sands Dense silty sands and sandy silts were generally encountered at depths of 30 to 35 feet to the extent of the borings Groundwater was not encountered during field activities The attached report indicates that groundwater is generally encountered at depths of 100 feet in the vicinity of the subject site Drilling at each location was continued until hydrocarbon contamination was no longer indicated by field instrumentation Accordingly, borings SBI, SB3, and SB4 were terminated at a depth of 40 feet while SB2 (W1) was advanced to 45 feet Wells W3 , W5, and W6 were installed to 40 feet, while W4 was installed to 30 feet and W2 was installed to 45 feet Wells Wl, W2, W3 were installed as 4-inch diameter vapor extraction wells , and wells W4, W5 , and W6 were installed as 2- inch diameter vapor inlet wells Although all of the wells were constructed using 0 020 slotted casing, the screened intervals in each well vary depending on well depth and field observations Appendix D in the attached report contains detailed well borings Boring and well locations are indicated on Figure 2 Canonie's report Three soil samples from each boring were submitted for analysis based on field screening and visual observation (Only 2 samples were submitted from W3 ) Each of the selected samples was analyzed for TPH, BTEX, and ethylene dibromide Results indicate that soil contamination is generally limited to the area of the