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Wm. I Hunter & Associates 2220 Loma Vista Dr <br /> Registered Geologists Sacramento, CA 95825 <br /> Petroleum & Mineral Appraisers (916) 972-7941 <br /> FAX (916) 972-1683 <br /> August 26, 1997 <br /> Steven Sasson, Sr RENS <br /> San Joaquin County PHS <br /> Environmental Health Division <br /> P 0 Box 388 <br /> Stockton, CA 0388 <br /> Ref Second Quarter 1997 Groundwater Monitoring Report for 2315 <br /> No Eldorado Street, Stockton <br /> Dear Mr Sasson, <br /> We have enclosed a copy of the field report, water analysis <br /> results, a gradient map, and maps showing lines of equal concen- <br /> trations of benzene, ethylbenzene, toluene, xylene, & TPHg for <br /> the above site. The work was performed on June 24, 1997, by <br /> Del-Tech Geotechnical Support Services as directed by our office <br /> PLATE T shows the potentiometric surface based upon the 6/24/97 <br /> sampling event . The gradient continues to be to the northeast at <br /> about 005 ' /ft ' <br /> ' The water table was measured at an average depth of 34 28 ' bgl, a <br /> drop of 0 35 feet since March <br /> TABLE A summarizes the results of all water analyses taken since <br /> monitoring began; it shows that MW-3 continues to record the <br /> highest levels of all measured compounds, with MW-4 the lowest <br /> A review of the total levels of BTEX from the 6 wells recorded <br /> during the last four samplings is summarized below <br /> COMPOUND 7/1996 11/ 1996 3/1997 6/1997 <br /> Units - ug/L <br /> BENZENE 51, 450 37, 237 52 , 270 40, 870 <br /> E BENZENE 4, 890 4, 666 4, 380 4, 416 <br /> TOLUENE 52, 800 29, 860 52, 400 26 , 372 <br /> XYLENE 28, 770 21, 430 25 , 590 20 , 480 <br /> TOTALS 137, 910 93, 193 134, 640 92 , 138 <br /> Total levels of TPH as gasoline decreased significantly between <br /> March and June, 1997 from 320 . 6 ug/L to 207 2 ug/L This <br /> decrease in TPHg mirrors a similar reduction in total levels of <br /> BTEX as shown above. This change may be due in part to natural <br /> attenuation, or the slight drop in the water table since the <br /> March, 1997 sampling <br /> r <br /> 1 <br />