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Wm. J. Hunter & Associates*, <br /> _ 2220 Loma Vista Dr <br /> Registered Geologists Sacramento, CA 95825 <br /> Petroleum & Mineral Appraisers 33 (916) 972-7941 <br /> rrn <br /> FAX (916) 972-1683 <br /> September 12, 1996 <br /> Michael Infurna, Sr. REHS <br /> San Joaquin County PHS <br /> Environmental Health Division <br /> 445 No San Joaquin Street <br /> Stockton, CA 95202 <br /> Ref SECOND QUARTER, 1996, GROUNDWATER MONITORING REPORT, 1876 <br /> Country Club Drive, Stockton; Site Code 1844 <br /> Dear Mr Infurna, <br /> We are enclosing the results of the eleventh groundwater measure- <br /> ments, sampling & laboratory results done on July 9, 1996, <br /> covering the above property. Included are copies of the field <br /> logs made by Del-Tech, a table summarizing sampling results, <br /> laboratory reports, a site map showing the pieziometric surface <br /> based on the 7/9/96 data, including directions of all of the <br /> hydraulic gradients measured to date We have also maps showing <br /> lines of equal concentrations of benzene, ethylbenzene, toluene, <br /> xylene & TPHg based on the most recent data Manifests for <br /> removal of purge water and soil drums are included at the back of <br /> this report <br /> A review of this work is discussed below <br /> 1 The water table was measured at an average depth of 15 40 , <br /> bgl , (--11 24 , msl, ) a rise of 2 . 98 , since the February sampling <br /> The lowest average depth was recorded at 22 .20 ' bgl in January, <br /> 1994 ; the highest was the latest event, July, 1996, at 15 40 ' <br /> bgl , a difference of 6 . 81 . The water table is currently about <br /> 3 ' above the screened intervals in the monitoring wells <br /> 2 . The hydraulic gradient as calculated from the latest event, <br /> (shown on PLATE I, ) is to the north/northeast at about . 00251 /ft <br /> This has been the predominant direction recorded since the start <br /> of the project . <br /> 3 A summary of all laboratory results of water samples taken <br /> since monitoring began is shown on TABLE I Laboratory reports & <br /> QA/QC results are included in the back of the report . MW-1 <br /> continues to show the highest levels of contamination Between <br /> the February & July samplings, benzene decreased from 10, 100 to <br /> 5475 ug/L, ethylbenzene decreased from 1020 to 645 ug/L, xylene <br /> from 4200 to 1665 ug/L, and TPHg from 53 to 32 mg/L MTBE was Op <br /> measured at 265 ug/L; it had not been analyzed in previous <br /> samplings . <br /> 1 <br />