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Harding;-awsan Associates <br /> the groundwater gradient at the former tank site is influenced by <br /> the domestic well usage. Seasonal fluctuations in the gradient <br /> are also likely to occur due to the Calaveras River located 7,000 <br /> feet north of the site, and the unlined Stockton diversion canal <br /> � . located 4,000 feet west of the site. <br /> We note that between July 3, and September 3, 1991, the <br /> groundwater level dropped between 2.3 and 4.1 feet. This <br /> declining water level leaves less that 3.5 feet of water in two <br /> of the three wells. <br /> DISCUSSION OF CHEMICAL RESULTS <br /> Soil <br /> y Two soil samples were submitted for chemical analysis from , <br /> F each monitoring well boring: one from a depth of 40.5 to 45.5 <br /> feet, near .the presumed historical high groundwater surface, and <br /> the other from 90 to 90.5 feet just above the current groundwater <br /> I surface, <br /> ny <br /> In al i six soil :samples analyzed, TPH as gasoline, benzene, <br /> xylenes, and ethylLenzene concentrations were below the <br /> — analytical detection limits. Toluene concentrations ranging from <br /> 3.4 to 5.5 parts per bil'.ior_ (ppb) were detected in five of the <br /> six samples. <br /> Groundwater <br /> Results of groundwater samples collected from WW-1 .on July <br /> 3, 1991 indicate thnt concentrations of benzene, ethylbenzene, <br /> r <br /> 10 <br /> F <br /> z- <br />