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1 f 1 <br /> Wm. J. Hunter & Associates ' 2220 Loma Vista Dr <br /> Registered Geologists r� �-� _ Sacramento, CA 95825 <br /> ``- 1� ! '� 916 972-7941 etroleum& Mineral Appraisers ( ) <br /> FAX (916) 972-1683 <br /> September 5, 1995 <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 . EIGHTH QUARTERLY GROUNDWATER MONITORING REPORT, <br /> 1876 Country Club Drive, Stockton, Site Code 1844 <br /> Dear Mr Infurna; a � <br /> We are enclosing the results of the ninth groundwater measure-- <br /> ments, sampling & laboratory results done on August 1, 1995, <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 3/23/1995 data, including directions of all of the <br /> hydraulic gradients measured to date . We have also included <br /> plates showing lines of equal concentrations of benzene & TPH-G <br /> • based on the most recent data <br /> A review of the most recent work is discussed below. <br /> 1 . The water table was measured at an average depth of 18 75 ' <br /> bgl, (-14 39 , msl, ) an average rise of 1 24 ' since the December <br /> sampling event . This is the highest depth to water since <br /> monitoring began in April, 1993 <br /> 2 The hydraulic gradient as to the north/northeast at about <br /> .30 /100 ' PLATE I shows the contours on top of the water table <br /> based upon the 8/1/1995 data. <br /> 3 . A summary of all laboratory results of water samples taken <br /> since monitoring began is shown on TABLE I That: data shows MW-1 <br /> continues to have the highest levels of BTEX & TPH-G, benzene was <br /> measured at 12, 000 ug/L, the highest level since the November, <br /> 1993 event . Xylene, at 8, 000 ug/L, was also the highest since <br /> November, 1993 MW--3 recorded significant levels of BTEX & <br /> TPH-G, but lower than MW-1 MW-2 was below detection limits for <br /> those constituents, the first time that has occurred since <br /> monitoring began MW-4 & MW-5 have not shown any contamination <br /> since they were installed in September, 1994 . <br /> 4 PLATE II shows lines of equal concentration of benzene based <br /> on the latest test results . It shows that the "zero" line has <br /> . shifted to the northwest; levels recorded in MW-3 are about 1/2 <br /> 1 <br />