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r 1 ` f 1 2 2 Preliminary Investigation and Evaluation On October 12, 1999, Ramage Environmental published Preliminary Investigation and Evaluation Report, which documented the results of soil and groundwater-grab samples collected from five (5) Geoprobe® soil borings (Figure 2) One boring (SB-1) drilled through the northern end of the former UST excavation was continuously cored to a depth of 43 feet The highest concentrations of diesel and gasoline hydrocarbons in soil were detected in samples collected from SB-1, located within the former UST excavation In the sample collected at 18 feet bgs from SB-1, Total Petroleum Hydrocarbons (TPH)-as-diesel was detected at a maximum concentration of 18,000 milligrams per kilogram (mg/kg), and TPH-as-gasoline was detected at 1,900 mg/kg Vertically, the extent of impacted sod beneath the former USTs was defined to a depth of between 35 and 43 feet bgs Laterally, the vertical extent of impacted sod appeared to be concentrated between 15 and 25 feet bgs, within the capillary fringe and zone of groundwater table fluctuation Total lead was not detected in the sod sample analyzed Concentrations of diesel and gasoline hydrocarbons were detected in the groundwater-grab samples collected at each of the five soil boring locations The highest concentrations were detected in the groundwater-grab sample collected from SB-1, located within the former UST excavation 2,700,000 micrograms per liter (pg/l) of TPH-as-diesel, 29,000 pgll of TPH-as- gasoline, 68 pgll of benzene, 7 5 pgli of toluene, 130 pgll of ethylbenzene, 210 pgll of xylenes, and 6 5 pgll of tertiary butanol The groundwater analytical results are summarized in Table 1 12 3 Installation of Three Monitoring_Wells On March 23, 2001, Ramage Environmental published Monitonng Well Installation Report, which documented the installation of three on-site groundwater table monitoring wells During drilling, saturated sod and groundwater were first encountered between 19 9 and 20 8 feet bgs The static depth to the groundwater table, as measured in the three groundwater monitoring wells, ranged from 18 47 to 18 56 feet bgs The resulting groundwater surface appeared as a regular plane dipping to the northwest at a gradient of approximately 0 0013 foot/foot The groundwater samples collected from all three of the groundwater monitoring wells contained detectable concentrations of petroleum hydrocarbons (Table 1) The oxygenate compounds and 1,2-dfchloroethane (1,2-DCA) were not detected in any of the groundwater samples 5 M