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30 SITE HISTORY <br /> 31 Previous Investigations <br /> In September 1991 as part of a facility upgrade, three underground storage tanks (USTs) and <br /> the pump islands were removed and replaced by Scott Company New USTs were installed <br /> within a new tank pit Results of the collection of seven soil samples from the UST excavation <br /> I and two samples from the pump island excavations indicated that the highest levels of <br /> petroleum hydrocarbons were 'found beneath the 6,000-gallon and the 8,000-gallon USTs, with <br /> concentrations of total petroleum hydrocarbons as gasoline (TPHg) detected at 8,900 parts per <br /> million (ppm) and 6,700 ppm, respectively Approximately 150 cubic yards of soil were removed <br /> from the UST and pump island excavations TPHg and benzene concentrations were reported <br /> in samples collected from the stockpiled excavation soil up to 2,700 ppm and 0 98 ppm, <br /> respectively This soil, along with soil removed from the new UST excavation, was reportedly <br /> 1 returned to the former UST excavation as backfill, which was remediated concurrently with the <br /> rest of the site (Canonie Environmental, April 1993) <br /> In August 1992, Environmental Control Associates, under the direction of Canonie <br /> Environmental, performed a soil gas survey (data only contained in Appendix A) Petroleum <br /> hydrocarbons were not detected in the 13 soil vapor survey samples (SG-1 through SG-13) <br /> The samples were collected at a maximum depth of 13 feet below ground surface (bgs) <br /> iAdvancement of the probes into deeper soil was inhibited by the presence of a hardpan layer at <br /> this depth (Canonie Environmental, April 1993) <br /> To further investigate the source of petroleum hydrocarbons in soil, Canonie Environmental <br /> oversaw the drilling of ten soil borings in the vicinity of the former USTs in September 1992 and <br /> October 1992 (SB-1 through SB-6, and W-1 through W-4) Three of the borings were <br />' completed as vapor extraction wells (W-1, W-2, and W-3), and three of the borings were <br /> completed as vapor-inlet wells (W-4, SB-5M-5, and SB-61W-6) Results of this investigation <br /> indicated that the soil contamination existed in the vicinity of the former USTs, with the majority <br /> of impacts reported at a depth of approximately 30 feet to 35 feet bgs (Canonie Environmental, <br /> April 1993) <br />' In December 1993, SEACOR supervised the drilling of five additional soil borings (SB-6, SB-7, <br /> SB-8, SB-9, W-8) to further delineate soil impacts in the vicinity of the former USTs Two of the <br /> borings were converted to vapor extraction/inlet wells (SB-8NV-7 and W-8) Elevated <br /> concentrations of TPHg were detected to the 30-foot (7,900 ppm), 44 5-foot (1,400 ppm), and <br /> 50-foot samples (1,700 ppm) collected from boring W-8 Results of the investigation indicated <br /> that the vertical extent of petroleum hydrocarbons had not been defined in the area of boring W- <br /> 8, and had not been laterally defined to the north and northeast (SEACOR, June 14, 1994) <br /> In December 1994, an additional site assessment was conducted by SECOR to further evaluate <br /> the extent of petroleum hydrocarbons in soil and groundwater at the site This investigation <br /> involved drilling five additional soil borings (MW-1, SB-101MW-2, MW-3, MW-4, MW-5/SB-1 1) to <br /> a depth of approximately 100 feet bgs Four of these borings were converted to groundwater <br /> monitoring wells (MW-1 through MW-4) Results of the investigation confirmed the presence of <br />' dissolved petroleum hydrocarbon impacts in each of the groundwater monitoring wells, and in <br />' Time Oil Asmt&SCM doc 3 March 17,2005 <br /> 770T 41658 00 0015 <br />