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2.0 SITE BACKGROUND The area surrounding the Site has been a mix of airport and agricultural usage for over 40 years The Site has been in existence since the early 1950s as an airplane fueling station and was expanded to its present size of approximately 25 acres in 1974 Fuel for the Site was originally stored in three 5,000-gallon steel USTs installed in the early 1950s and removed in 1990 The I USTs were oriented east-west and rested on a six-inch-thick concrete slab The slab still remains in place at a depth estimated to be 11 feet bos The fuel dispensers were originally located on the north side of the USTs During the 1974 expansion/modernization, the dispensers were relocated 30 feet to the east Aviation gasoline was reportedly stored in the original USTs until the early 1960s, when turbine-powered aircraft began replacing older piston powered planes From approximately 1962 until 1989, the tanks contained JP-4 Fuel loss from the original USTs was not detected during inventory monitoring, which was accomplished by weekly sticking There is no record of a precision leak test having been ' performed on the three USTs There is no record of any repairs of the former USTs, however, as described previously the dispensers were relocated 30 feet to the east during the 1974 expansion 2.1 Underground Storage Tank Removal The three 5,000-gallon USTs formerly on site as shown in Figure 2 were taken out of operation in 1989 and removed in January 1990 The former USTs reportedly appeared intact and were not leaking at the time of removal Blaine Tech Services, Inc , collected five soil samples (1 through 5) from beneath the tanks at the time of removal Samples 1 through 4 were collected along the edge of the concrete slab, Sample 5 was collected beneath the slab after a hole was cored through it Samples were reportedly collected from 2 75 feet below the concrete slab, approximately 13 to 14 feet bgs Analytical results from Sample I indicated 1,500 milligrams per kilogram (mg/kg) total petroleum hydrocarbons as diesel (TPH-D) and 1,600 mg/kg TPH as jet fuel, Sample 4 contained 3,500 mg/kg TPH-D and 5,100 mg/kg TPH as jet fuel TPH-D, TPH as jet fuel, BTEX were not detected in the other samples Records related to the original UST piping were not available, but because the dispensers were near the USTs, the piping was most likely minimal, hence no additional soil sampling was conducted As soil adjacent to the USTs was impacted with petroleum hydrocarbons, an Unauthorized Release Form (No 90-U11) was completed and submitted to the PHS/EHD on January 31, 1990 Proposition 65 notification (No 90-022) was also submitted at this time Sample locations and analytical results as presented by previous consultants for the soil samples collected during the UST removal and subsequent investigations are detailed in Versar's Site Investigation Workplan, Idated August 2, 1995 P IDSAISTOCKTOM337200111STQTR RPT