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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 This sample contained 2,700,000 micrograms per liter (jig/1) of TPH-as-diesel, 29,000 n/l of TPH-as-gasoline, 68 µgll of benzene, 7 5 µg11 of toluene, 130 µg/l of ethylbenzene, 210 µg11 of xylenes, and 6 5 µg/l of tertiary butanol MTBE, DIPE, ETBE and TAME were not detected in ' any of the groundwater-grab samples These groundwater-grab sample results are summarized in Table 2 ' 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 The objectives of ' this investigation were to confirm concentrations of petroleum hydrocarbons in groundwater and to establish a groundwater monitoring capability at the site During drilling, saturated soil and groundwater were first encountered between 19 9 and 20 8 feet bgs Eight days later, 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 groundwater surface elevation ranged from a high of 18 18 feet above mean sea level (msl) at MW-2 to a low of 18 10 feet above ms] at MW-1 The resulting groundwater surface appeared as a regular plane dipping ' to the west at a gradient of approximately 0 0013 foot/foot ' Sod and groundwater beneath the site appeared to be impacted by diesel and gasoline hydrocarbons, in relatively equal proportion Concentrations of benzene were not present or significant in soil and were relatively low in groundwater Except for a couple of trace detectable ' concentrations, the oxygenate compounds and 1,2-Dichloroethane (1,2-DCA) were not found in sod or groundwater ' The groundwater samples collected from all three of the groundwater monitoring wells contained detectable concentrations of petroleum hydrocarbons Maximum concentrations in groundwater ' included 15,000 µg11 of TPH-as-diesel, 12,000 µg/1 of TPH-as-gasoline, 19 µg/l of benzene, 5 6 µg/l of toluene, 1,300 µg/1 of ethylbenzene, and 52 µg/l of xylenes The oxygenate compounds and 1,2-DCA were not detected in any of the groundwater samples Petroleum hydrocarbons concentrated to groundwater near the source appeared to have migrated preferentially to the northwest and west, in an apparent downgradient direction 5 1