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� ` may^. _ -� � � _ d �. .F '�� • h .y""2 a�� p �% �- <br /> Wi1'� �` xV +l+- F T � r 5- _ mM � ' .p `NC• _ � u C ` <br /> J <br /> Groundwater beneath the Holt Brothers facility is apparently confined or semi. <br /> confined. as evidenced by shallower static water levels seen in the monitoring <br /> wells than was first encountered during initial drilling, Due to the <br /> heterogeneity of the uncP.rlying strata it is possible that groundwater elevation <br /> beneath the tank excavation areasis locally higher due to improved vertical <br /> Permeability, This would allow for vertical migration of contaminants downward, <br /> but would also allow for a higher head beneath the excavation area. This higher <br /> head, or 'hole" in the confined aquifer, could prevent further downward and <br /> lateral migration of the contaminants. Lack of migration of contaminants might <br /> also be attrinutable to a low volume of contaminant release from the former <br /> tanks, though actual volumes released are unknown. <br /> 7.0 CONCLUS 0 iS <br /> $oil contamination at the Holt Brothers facility appears to be liLaited both <br /> vertically and horizontally to an area within the general vicinity of the former <br /> tank excavation area. Though a zero-contamination line for sois was not <br /> delineated south-southeast of the main tank excavation (beyond B-5 and MW-6), <br /> the sail cora-amination appears toui <br /> q skLy attenuate away from the excavation pit. <br /> Groundwater contamination is limited to within the immediate vicinity of the <br /> former tank'excavation areas, <br /> i. <br /> Figures ! to 4 and Appendices A to C are attached and complete this report. <br /> Respectfully submitted, <br /> w LAMES MOORE <br /> 111L <br /> Allen Kearns <br /> Associate <br /> Z, <br /> uane C, Balch <br /> _ <br /> Project Manager <br /> aAC03,001 10 . <br /> November 1989 <br />