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Wm. J. Hunter & Associates 2220 Loma Vista Dr <br /> Segistered Geologists Sacramento, CA 95825 <br /> Oetroleum& Mineral Appraisers (916) 972-7941 <br /> FAX (916) 972-1683 <br /> r <br /> April 12, 1993 <br /> n F.UE I V E D <br /> Michael Collins, RENS APR 16 1993 <br /> San Joaquin County Health Department <br /> Environmental Health Division LNVIRUNMENTAL HEALTH <br /> 445 North San Joaquin Street PERMIT/SERVICES <br /> Stockton, Ca 95202 <br /> Ref : Quarterly Groundwater Monitoring Report for 814 E. Charter <br /> Way, Stockton -- Site Code 10761 <br /> Dear Michael ; <br /> I am enclosing a copy of the field report, water analysis, and <br /> gradient map for the above property. The work was performed on <br /> March 3, 1993 by Del-Tech Geotechnical Support Services as <br /> directed by my office. <br /> The map also shows the gradient as measured in October , 1992, <br /> shortly after the monitoring wells were placed. bath measure- <br /> ments indicate a northeasterly direction , which agrees quite well <br /> (0 <br /> with data obtained from the Exxon Gasco property nearby. <br /> It is interesting to note the differences in levels of contami- <br /> nation as measured in the 3 wells between last October ano the <br /> current work; they are summarized below for your information. <br /> 5UBSTANCE MW-1 MW-2 MW-3 <br /> Results 1.0/92 3/93 10/9 21 3/91 10/92 3/93 <br /> an ug/L <br /> Benzene ND ND .7. 0 3,. C� 19. ;17. 0 <br /> Toluene ND ND i .6� '1 .9' ND 7. 4 <br /> Ethylbenzene ND ND ND 0. 3- \ ND 0. 7, <br /> Xylene ND ND ND 1 .0 ND i. 3 <br /> TPP-G r6�, 200 47Of 500-' \12oo" <br /> The levels of contamination increased in all 3 wells between the <br /> two tests, except for a slight decrease in Benzene in MW-2 & :.. <br /> This suggests either an offsite source, or the rise in the ground <br /> water level , (2' between October & March, ) has caused some <br /> infusion of products from the soil . Although TF'H--G was detected <br /> in 3 soil borings at 303 , 35 & 40 " at levels ranging from . 54 to <br /> 5. 85 mg/kg, it does not appear likely that all of the gasoline <br /> fraction measured could be dissolved that readily from the soil . <br /> Comments on the laboratory analysis worksheets mention that the <br /> Constituents found in the samples ran are not those usually found <br /> in gasoline. We may request permission to obtain water samples <br /> 110 <br /> `n1 <br /> 41{il \W11� <br />