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Concentrations of diesel and gasoline hydrocarbons were detected in the groundwater-grab ' samples collected at each of the five sal boring locations The highest concentrations were detected in the groundwater-grab sample collected from SB-1 This sample contained 2,700,000 ' micrograms per liter (µg11) of TPH-as-diesel, 29,000 µg/l of TPH-as-gasoline, 68 µg11 of benzene, 7 5 �Lg/l of toluene, 130 µg11 of ethylbenzene, 210 µg/l 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 msl 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 Soil and groundwater beneath the site are impacted by diesel and gasoline hydrocarbons, in ' relatively equal proportion Concentrations of benzene are not present or significant in sod and are relatively low in groundwater Except for a couple of trace detectable concentrations, MTBE, DIPE, ETBE, TAME, TBA and 1,2-DCA are not present in sod or groundwater The soil sample analytical results are summarized in Table 1, and the groundwater analytical results are summarized in Table 2 T g samples The groundwater les collected from all three of the groundwater monitoring wells contained p detectable concentrations of petroleum hydrocarbons Maximum concentrations in groundwater include 15,000 µg/1 of TPH-as-diesel, 12,000 µg/l of TPH-as-gasoline, 19 µg/l of benzene, 5 6 µg11 of toluene, 1,300 µg/l of ethylbenzene, and 52 µg/l of xylenes The gasoline oxygenate ' compounds and 1,2-DCA were not detected in any of the groundwater samples Petroleum hydrocarbons concentrated in groundwater near the source appear to have migrated preferentially to the northwest and west, in an apparent downgradEent direction 6 1