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Wm. J. Hunter & Associates 2220 Loma Vista Dr Registered Geologists Sacramento, CA 95825 Petroleum & Mineral Appraisers (916) 972-7941 << FAX (916) 972-1683 January 13 , 1997 Steven Sasson, Sr REHS San Joaquin County PHS ' Environmental Health Division P b Box 388 Stockton, CA 0388 ' Ref Fourth Quarter 1996 Groundwater Monitoring Report for 2315 No. Eldorado Street, Stockton ' Dear Mr Sasson, We have enclosed a copy of the field report, water analysis results, a gradient map, and maps showing lines of equal concen- trations of benzene, ethylbenzene, toluene, xylene, & TPHg for the above site The work was performed on November 13 , 1996, by Del-Tech Geotechnical Support Services as directed by our office . IPLATE I Shows the potentiometric surface based upon the 11/13/96 sampling event The gradient continues to be to the northeast at about 005 ' /ft ' , or 26 ' /mile The water table was measured at an average depth of 40 .44 ' bgl, a drop of almost 3 feet since the July, 1996 sampling ITABLE A summarizes the results of all water analyses taken since monitoring began, it shows that MW-3 has the highest levels, with I MW-5 second highest, and MW-1 & MW-4 the lowest A review of that table shows that there has been a significant reduction in levels of BTEX between the July & November samplings total levels of those compounds in the six wells 2n July & November are summarized below for your information COMPOUND July, 1996 November, 1996 CHANGE Units - ug/L BENZENE 51, 450 37, 237 (14, 213) E .BENZENE 4, 890 4, 666 (224) TOLUENE 52, 800 29, 860 (22, 940) XYLENE 28 , 770 21, 430 (7 , 340) TOTALS 137, 910 93, 193 (44, 717) ITotal levels of TPH as gasoline increased slightly between July & November, from 241 . 6 ug/L to 297 . 8 ug/L IPLATES II, III, IV, V, & VI show lines of equal concentration of benzene, ethylbenzene, toluene, xylene, & TPHg based upon the 1 1 f