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Wm. J. Hunter & Associates 2220 Loma Vista Or <br /> Registered Geologists Sacramento, CA 95825 <br /> Petroleum& Mineral Appraisers (916) 972-7941 <br /> FAX (916) 972-1683 <br /> June 28, 1996 <br /> Margaret Lagorio, Sr REHS <br /> San Joaquin County PHS <br /> Environmental Health Division <br /> P 0 Box 388 <br /> Stockton, CA 95201-0388 <br /> Ref - Second quarterly groundwater monitoring report for 1401 W <br /> Fremont St , Stockton, Site Code 1782 <br /> We are enclosing a report covering the third sampling event at <br /> the above site, Valley Wholesale Drug Co It includes the field <br /> logs, laboratory results of water analyses, and maps showing the <br /> hydraulic gradient (s) and approximate lines of equal concentra- <br /> tions of benzene, ethylbenzene, toluene, xylene, & TPHg based on <br /> the latest data The field work was done on March 25, 1996, by <br /> Del-Tech Geotechnical Support Services as directed by our office <br /> PLATE I shows the hydraulic gradient based upon the 3/25/1996 <br /> sampling event . It has shifted to the south at about 008 ' /ft <br /> • The water table has risen about 42 ' since the December sampling, <br /> to an average of 8 . 70 ' bgl <br /> The results of the laboratory analyses of water samples taken <br /> from the three monitoring wells in August & December are shown on <br /> TABLE I The levels of BTEX & TPHg have increased significantly <br /> since the December sampling event The reason for this is not <br /> readily apparent, since MW-1 was not in a downgradient position <br /> from the removed UST during the March sampling Levels measured <br /> in MW-3 were not significantly different than those from the <br /> December sampling, although the well was directly downgradient in <br /> March This suggests that the gradient as measured may be <br /> transient in nature, and of short duration This shift was also <br /> observed during sampling performed about 10 days earlier at 913 <br /> W. Fremont Street, about 5 blocks to the east of this site BTEX <br /> & TPHg were below detection levels in MW-2 , which is the farthest <br /> from the removed UST, and to date has not been downgradient <br /> PLATES II through VI show the approximate lines of equal concen- <br /> trations of BETX & TPHg based upon the March, 1996 laboratory <br /> results As in prior data, concentrations of all components <br /> increase in a westerly direction <br /> SUMMARY & CONCLUSIONS <br /> The results of work performed to date on this site can be briefly <br /> summarized as follows <br /> 1 <br />