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Laboratory results indicated that concentrations of petroleum hydrocarbons were detected in the <br /> 1 soil samples collected from beneath the northern and central USTs Concentrations of petroleum <br /> hydrocarbons included 9,900 milligrams per kilogram (mg/kg) TEPH beneath the northern weed <br /> oil UST and 18 mg/kg NPH from beneath the central gasoline UST Petroleum hydrocarbons <br /> were not detected in the soil sample collected from beneath the southern weed oil UST <br /> ' 12.2 Preliminary Investigation and Evaluation <br /> On October 12, 1999, Ramage Environmental published Preliminary Investigation and Evaluation <br /> ' Report, which documented the results of soil and groundwater-grab samples collected from five <br /> (5) Geoprobe® soil borings (Figure 2) One boring (SB-1) drilled through the northern end of the <br /> former UST excavation was continuously cored to a depth of 43 feet Groundwater levels <br /> measured in each of the soil borings ranged from 18 7 to 21 0 feet bgs <br /> The highest concentrations of diesel and gasoline hydrocarbons in soil and groundwater were <br /> detected in samples collected from SB-1, located within the former UST excavation In the soil <br /> 1 sample collected at 18 feet bgs from SB-1, Total Petroleum Hydrocarbons (TPH)-as-diesel was <br /> detected at a maximum concentration of 18,000 mg/kg, and TPH-as-gasoline was detected at <br /> 1,900 mg/kg Vertically, the extent of impacted soil beneath the former USTs appeared to be <br /> defined to a depth of between 35 and 43 feet bgs Laterally, the vertical extent of impacted soil <br /> appeared to be concentrated between 15 and 25 feet bgs, within the capillary fringe and zone of <br /> groundwater table fluctuation These soil sample analytical results are summarized in Table 1 <br /> Concentrations of diesel and gasoline hydrocarbons were detected in the groundwater-grab <br /> samples collected at each of the five soil boring locations The highest concentrations were <br /> detected in the groundwater-grab sample collected from SB-1 This sample contained 2,700,000 <br /> micrograms per liter (µg11) of TPH-as-diesel, 29,000 µg11 of TPH-as-gasoline, 68 µg/1 of benzene, <br /> 7 5 µg11 of toluene, 130 µg/l of ethylbenzene, 210 µg/I of xylenes, and 6 5 µg/l of tertiary butanol <br /> 1 (TBA) Methyl tertiary butyl ether(MTBE), di-isopropyl ether(D1PE), ethyl tertiary butyl ether <br /> (ETBE) and tertiary amyl methyl ether (TAME) were not detected in any of the groundwater-grab <br /> samples The groundwater-grab sample results are summarized in Table 2 <br /> 1 <br /> 1 <br /> 1 6 <br /> i <br /> 1 <br /> 1 <br />