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I - v S-�{%7FGTr+YM�tx>46+.4'.:eWl^.✓t rf .'+i`� iZY, q, v^ wP �-r�� �� aY.3» y"6f.- NMi4 F' .7G`". _ a <br /> iF <br /> £ In summary, significant levels of diesel residues and low levels of aromatic <br /> volatile compounds were found under the former :',tank site. The extent of soil <br /> contamination Is less than 10 feet laterally from the edge of the tank site. It <br /> appears that contaminants have moved vertically. <br /> Based on the results of the soil Investigation. It is proposed to installl a E <br /> boring to the water table. A groundwater elevatlon ll for the Spring of 1986 , <br /> prepared by San Joaquin County Flood Control District (attachment x}2) shows that <br /> the regional groundwater gradients in the areat,are generally northeasterly. i <br /> + Therefore, it Is recommended that the boring t4 the water table be located 10 1 <br /> 1 feet northeast of the tank excavation. This would be in the downgradlent r <br /> l { <br /> � direction and yet close enough to the tank site to allow the observation of any <br /> 1 diesel products floating on the water table surface.11 From the results of the j <br /> soil Investigation of 3/30/87. it Is known that soils 10 ft. from the excavation <br /> are not contaminated and that drilling througrill soils with a hollow stela <br /> + auger would not Introduce contaminants to the groundwater. The boring will be <br /> completed as a well with sufficient screen length to�kallow the observation of } <br /> any formation of a separate phase. The proposed location of the boring will not <br /> t Impede any remedial action that may be selected for the contaminated soil under r <br /> the tank site. <br /> It Is our Intent to proceed with the boring to�the vill table as soon as # j <br /> scheduling permits. If you have any comments, please call me at 415/231-1242 1 <br /> t or Frank Yoneshige at 209/466-9580. ! <br /> r <br /> Sincerely, <br /> i Larry E. It <br /> Senior �Hydrogeologist <br /> I LEH:lb !f s <br /> Attachments <br /> f <br /> cc: Rex Defenbaugh j{ <br /> i Frank Yonechiye 'I <br /> P <br /> 1 ii F <br /> ' l <br /> N <br /> n <br /> 1 <br /> ilk <br /> 1 <br /> � r <br /> 0 !� <br />