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A conversation with Mr. Dale Kuenzli on June 25th indicates <br /> that the tanks have been petro tested as being tight, therefore <br /> it appears the contamination is due to the older tank. <br /> .�' <br /> Areal Extent of Contamination <br /> ' The investigation to identify the areal and vertical extents <br /> of contamination consisted of Placingborings gs on a 20 grid <br /> pattern centered on the previous high readings located in <br /> B--4 (p) . To differentiate <br /> f all previous borings will be followed <br />' with <br /> (p) to indicate previous. The borings were initially taken <br /> eastward from B-4 (p) as this was the expected hydrogeologic <br /> gradient due to topography and the location of a small creek at <br /> the eastern border of the property (see boring plan) . <br /> r � <br /> In order to find the eastern extents, of contamination, f <br /> borings were taken in a relatively straight line eastward from <br /> B-4 (p) . The field instrument, an HNU photoianization detector <br /> equipped with a 10.2 eV probe indicated that the highest levels <br /> of contamination occured in a zone approximately 11 to 15 feet <br /> below the ground surface. The contaminant plume appears to be <br /> thickesthave <br /> ( the greatest vertical area) closer to the tank <br /> installation. The contamination was also investigated to the <br /> north and south and delineated to be an approximately 60 foot by <br /> 75 foot area. Borings adjacent to the tank installation to the <br /> west and north did not indicate any contaminant presence. B-3(p) <br /> r <br /> indicated some small amount of contamination to the south, <br /> however other southerly borings did not indicate contaminant <br /> presence. <br /> Page 33 <br /> 72 <br />