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Wm. J. Hunter & Associates 2220 Loma Vista Dr Registered Geologists Sacramento, CA 95825 . Petroleum & Mineral Appraisers (916) 972-7941 FAX (916) 972-1683 January 29, 1996 i Margaret Lagorio, Sr REHS San Joaquin County PHS Environmental Health Division P 0 Box 388 Stockton, CA 95201-0388 Ref - First quarterly groundwater monitoring report for 1401 W Fremont St , Stockton, Site Code 1782 We are enclosing a report covering the second sampling event at the above site, valley wholesale Drug Co It includes the field logs, laboratory results of water analyses, and maps showing the hydraulic gradient (s) and approximate lines of equal Concentra- tions of benzene, ethylbenzene, toluene, xylene, & TPHg based on the latest data. The field work was done on December 7, 1995, by Del-Tech Geotechnical Support Services as directed by our office PLATE I shows the hydraulic gradient based upon the 12/7/1995 sampling event . It is to the northwest at about 0051 /ft Both • the direction and slope of the gradient are almost identical to the August, 1995 sampling The water gable has dropped an average of 1 .17 ' between the August (7 951 ) and December (9 121 ) sampling events The results of the laboratory analyses of water taken from the three monitoring wells in August & December are shown on TABLE I Benzene in MW-1 decreased from 400 ug/L in August to 41 ug/L in December; it dropped from 13 0 ug/L to 3 .2 ug/L in MW-2 , but increased from 28 ug/L to 45 ug/L in MW-3 Ethylbenzene in MW-1 increased from 78 to 110 ug/L, was ND both times in MW-2 , and decreased from 34 to 29 ug/L in MW-3 Toluene in MW-1 increased slightly from 220 to 250 ug/L, decreased in MW-2 from 1 2 ug/L to ND, and decreased in MW-3 from 22 to 6 4 ug/L Xylene decreased an all three wells from 400 to 260 ug/L in MW-1, from 5 1 ug/L to ND in MW-2, and from 380 to 89 ug/L in MW-3 TPH as gasoline increased from 1 9 to 17 mg/L in MW-1, was ND in both samplings from MW-2, and decreased from 4 . 1 to 2 5 mg/L 3n MW-3 . It is expected that MW-1 would record the highest levels of contamination since it is in a downgradient position from the site of the removed UST' s MW-2, which is the farthest from the tank site, and essentially on strike with the hydraulic gradient, has revealed the lowest levels of contamination This agrees with data obtained from prior investigative work. Levels in MW-3, which is in an upgradient position, have generally decreased since the August sampling This is what would be 1