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2220 Loma Vista Dr <br /> Wm. J. Hunter & Associates � f+�t !{ �; {'rte. P,EA �tl <br /> Registered Geologists �� ��- Sacramento, CA 95825 <br /> `4w -etroleum& Mineral Appraisers o , "� <br /> � �.i� �7 � (916) 972-7941 <br /> j; 33 FAX (916) 972-1683 <br /> March 17, 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- SIXTH QUARTERLY GROUNDWATER MONITORING REPORT, 1876 Country <br /> Club Drive, Stockton; Site Code 1844 <br /> Dear Mr. Infurna; <br /> We are enclosing the results of the seventh groundwater measure- <br /> ments, sampling & laboratory results done on December 29, 1994, <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 piezzometric surface <br /> based on the 12/29/94 data, including directions of all of the <br /> hydraulic gradients measured to date. We have also included two <br /> plates showing lines of equal concentrations of benzene & TPH-G <br /> based on the most recent data. <br /> 1� A review of the most recent work is discussed below- <br /> 1 . The water table was measured at an average depth of 22. 27' <br /> bgl, (-18. 11' msl, ) up slightly since the September sampling. <br /> The maximum change in elevation has been about 1 5' since mon- <br /> itoring began. <br /> 2 The hydraulic gradient continues to be in a northeasterly <br /> direction at about . 25' /1000 . PLATE I shows the contours on top <br /> of the water table based upon the 12/29/94 data The direction <br /> has not changed significantly during the last three events Only <br /> the 1/26/94 data showed a direction slightly to the east of due <br /> north, all the rest have been in the northeast and southeast <br /> quadrants- There have been no data indicating a westerly <br /> gradient. The newly placed monitoring well #4 is in a <br /> downgradient positiLon from the removed UST' s <br /> 3 A summary of all laboratory results of water samples taken <br /> since monitoring began Ls shown on TABLE I. That data shows MW-1 <br /> continues to have the highest levels of BTEX & TPH-G; MW-3 has <br /> the second highest, and MW-2 the lowest. This ratio has remained <br /> consistent since monitoring began. MW-4 & MW-5 have not shown <br /> any contamination 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. As in previous reports, it continues <br /> to show that the highest level is in MW-1, which is on strike <br /> 1 <br />