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2220 Loma Vista Dr <br /> Wm. J. Hunter & Associates E A; ?! Sacramento, CA 95825 <br /> Registered Geologists _- _ (916) 972-7941 <br /> Petroleum & Mineral Appraisers FAX (9 16) 972-1683 <br /> 4� i"' "' 110 33 <br /> January 25, 1996 <br /> Ron Rowe, Sr REHS <br /> San Joaquin County PHS <br /> Envrironmental Health Division <br /> P O Box 388 <br /> Stockton, CA 95201-0388 <br /> Ref First Quarterly Groundwater Monitoring report for 1211 South <br /> Turnpike Road, Stockton, Site Code 1788 <br /> Dear Mr Rowe, <br /> We are enclosing a copy of the field report, laboratory results <br /> of water analyses, and maps showing the hydraulic gradient and <br /> lines of equal concentrations of benzene, ethylbenzene, <br /> toluene, <br /> xylene, and TPHg based on the latest data The field work was <br /> conducted on December 1, 1995 by Del-Tech Geotechnical Support <br /> Services as directed by our office Due to ma3or equip <br /> nt <br /> problems, Del-Tech was unable to perform the work in October as <br /> originally scheduled <br /> • The attached PLATE I shows the hydraulic gradient based on the <br /> 12/1/1995 sampling event , it is to the northeast . The July <br /> gradient direction, shown below the latest data, indicates the <br /> gradient has not changed direction during the 5 months between � ki <br /> samplings The gradient is very flat, at about . 003 ' /ft - t� <br /> The results of the water analyses taken in July & December are <br /> summarized on TABLE I The changes in levels of contamination <br /> between the two sampling events are interesting In MW-1, <br /> benzene, toluene, & xylene decreased on the order of one-half in <br /> the December sampling, ethylbenzene increased about 20% , and TPHg <br /> increased almost three-fold In MW-2 , benzene increased almost <br /> 300%, ethylbenzene 16000 , and toluene about 2500% Xylene <br /> decreased slighty, (from 110 ug/L to 95 ug/L, ) and TPHg increased <br /> from 2 7 mg/L to 3 8 mg/L In MW-3 , benzene increased from 310 <br /> ug/L to echanges bannotall <br /> beother <br /> expla�nedunds baseddecreased <br /> l�m limited <br /> reason <br /> for then ges <br /> information available to date . <br /> PLATES II thru VI show lines of equal concentrations of BETX & <br /> TPHg based on the December water analyses Levels of benzene, <br /> (PLATE II , ) ethylbenzene, (PLATE III , ) & toluene, (PLATE IV, ) <br /> increase to the north, while the hydraulic gradient is indicated <br /> to be to the east Levels of xylene & TPHg, (PLATES V & VI , ) <br /> radient <br /> incease <br /> own, additionaldirection <br /> reason <br /> monitoringevents <br /> • foor <br /> these <br /> thus <br /> 1 <br />