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contained detectable concentrations of benzene,toluene, ethylbenzene, and <br /> xylenes (BTEX). BTEX was not detected in the other sample, and total <br /> petroleum hydrocarbons as gasoline (TPHG) was not detected in either <br /> sample. In September 1988, the area was overexcavated. Confirmation soil <br />' samples were collected from the bottom of the excavation. Petroleum <br /> hydrocarbons were not detected in any of the confirmation soil samples <br /> collected during this overexcavation activity. <br /> 2.3 Ground-water Characterization <br /> Ground-water sampling and analysis has been conducted at the site since <br /> January 1987. Following confirmation of ground-water impact, <br /> overexcavation activities were performed in September 1987 (as discussed <br />' in preceding sections of this document) to remove a potential source of <br /> additional ground-water impact. <br />' Wells MW-1 , MW-2, and MW-3 were installed in January 1987; however, <br /> well MW-1 was damaged and well MW-2 was removed in September 1987 <br /> during the overexcavation of the impacted soil near the former tank <br />' complex. Wells MW-4 and MW-5 were installed in September 1987. Since <br /> that time, the ground-water elevation has dropped, and these wells, as well <br /> as well MW-3, are now dry. To continue with ground-water monitoring, <br /> deeper wells (MW-9, MW-10, and MW-11) were installed in March 1990. <br /> Concentrations of petroleum hydrocarbons in wells MW-9, MW-10, and <br />' MW-11 have historically been relatively low or nondetectable. Since <br /> March 1990, 14 samples have been collected from wells MW-9, MW-10, <br /> and MW-11. (Vine of the samples did not contain detectable concentrations <br />' of petroleum hydrocarbons. Toluene was not detected in any of the other <br /> five samples; xylenes were detected in one of the samples; benzene was <br /> detected in two samples; and total petroleum hydrocarbons were detected <br />' in three samples. <br /> Based on ground-water flow directions and gradients reported by Elder <br />' Engineering, Inc.,the predominant flow direction of first-encountered ground <br /> water was to the northwest with a gradient of 0.0075 foot per foot. This <br /> information is for the time period from March 29, 1990, to June 10, 1991 . <br /> pjO\Of9010f900020.1 ag 2 - 2 Rev. 0 December 15, 1992 <br />